04 July 2026

Building an A Level Platform Game Project — Part 1: Planning the Game and Setting Realistic Success Criteria

Every good programming project starts with an exciting idea.

Every successful A Level Computer Science project starts with a controlled idea.

That distinction matters.

When students say they want to write a game, they often imagine the finished product first: animated characters, moving enemies, several levels, sound effects, menus, high scores and perhaps even a storyline. That is a perfectly natural way to think as a player. It is not the best way to think as a programmer.

For this project series, we are going to build a simple retro-style platform game. The aim is not to create the next commercial console game. The aim is to produce a working, expandable, testable game that could be used as a model for an A Level project.

This first article is about planning.

Before we write a single line of code, we need to decide what the game is, what it will do, what it will not do, how success will be measured and how the student can collect evidence along the way.

That planning stage may not feel as exciting as making a character jump across the screen, but it is one of the most important parts of the whole project.

Why Planning Matters Before Programming

Many students are tempted to start coding immediately.

They open Python, Pygame, JavaScript, Unity, Godot or another development environment and begin experimenting. There is nothing wrong with experimentation, but it is not the same as a planned project.

A Level project work needs evidence. It needs to show that the student has thought about the problem, considered the user, designed a solution, tested it and evaluated the final outcome.

A game project is not marked simply because it looks fun. It needs to show computational thinking.

That means the student must be able to explain:

what the game is intended to do
who the game is for
what the main features are
which features are essential
which features are optional
how the game will be tested
what makes the project successful
how the design changed during development

Without planning, the project can quickly become a collection of half-finished features.

With planning, even a simple game can become a strong piece of evidence.

The Basic Game Idea

The project we are going to design is a simple 2D platform game.

The player controls a character who can move left and right, jump onto platforms, avoid hazards, collect items and reach an end point.

The game will be retro in style. That is deliberate.

A retro-style game allows us to focus on programming rather than complex artwork. The graphics can begin as coloured rectangles or simple sprites. The technical challenge will come from the movement, gravity, collision detection, level design, scoring and testing.

A simple project description might be:

The aim of the project is to create a 2D platform game in which the player controls a character, moves through levels, jumps between platforms, avoids hazards, collects points and reaches a finish point. The game will include increasing difficulty, clear win and lose conditions, and a scoring system.

That is clear, achievable and expandable.

It gives us enough to build a good project without becoming impossible.

What the Game Is Not

This is just as important as deciding what the game is.

The game is not:

a 3D game
an online multiplayer game
a realistic console-style game
a huge open-world adventure
a game with dozens of levels
a project mainly about graphics
a project copied from a tutorial without understanding

This matters because students often lose control of projects by adding too much too early.

A successful project is not the one with the longest feature list. It is the one where the features actually work and are properly explained.

A small, complete game is much stronger than an ambitious unfinished one.

Starting With the Minimum Viable Game

A useful project design technique is to begin with the smallest version that can be called a game.

This is sometimes called a minimum viable product, or MVP.

For our platform game, the minimum viable version would include:

a game window
a player character
left and right movement
gravity
jumping
at least one platform
collision detection with the platform
a way to win or finish the level
a way to lose or restart

That is enough to make a playable first version.

It may look basic, but it proves that the core mechanics work.

Once that is working, the student can add features gradually.

Essential, Desirable and Extension Features

A good way to keep the project under control is to divide features into three categories.

Essential Features

These are the features the game must have.

Without these, the project does not really work.

For this platform game, essential features could include:

player movement left and right
jumping
gravity
platforms
collision detection
hazards or obstacles
a scoring system
a start position
an end point
win and lose conditions
basic testing evidence

These should be completed first.

Desirable Features

These are features that would make the game better, but the game can still function without them.

Examples include:

collectable coins or stars
multiple levels
lives
a start menu
a pause screen
a high score table
simple sound effects
improved graphics
moving enemies
moving platforms

These are useful because they provide development opportunities once the main game works.

Extension Features

These are more advanced features that should only be attempted if the core project is already working.

Examples include:

level editor
user-created levels
saved progress
difficulty settings
animated sprites
different player characters
enemy artificial intelligence
timed challenges
file-based level loading
controller support

These could be excellent additions, but they should not be allowed to damage the main project.

A sensible student should not begin with extension features. They should earn the right to add them by first completing the essential game.

Setting Realistic Success Criteria

Success criteria are one of the most important parts of project planning.

They define what the program should do. They also provide a basis for testing and evaluation.

Weak success criteria are vague.

For example:

The game should be fun.
The graphics should be good.
The player should be able to move.
The game should have levels.

These are not useless, but they are not precise enough.

Better success criteria are specific and testable.

For example:

The player can move left and right using keyboard input.
The player falls downwards when not standing on a platform.
The player can jump only when standing on a platform.
The player cannot pass through solid platforms.
The player loses a life when touching a hazard.
The score increases when the player collects an item.
The level ends when the player reaches the finish point.
The game displays a final score at the end of the level.

These can be tested.

That is the key.

If a success criterion cannot be tested, it is probably not clear enough.

Example Success Criteria for the Platform Game

Here is a possible set of success criteria for the first version of the project.

Player Movement

The player can move left when the left arrow key is pressed.
The player can move right when the right arrow key is pressed.
The player stops moving horizontally when no movement key is pressed.
The player cannot move beyond the edge of the game screen.

Jumping and Gravity

The player falls when not standing on a platform.
The player can jump from the ground or a platform.
The player cannot repeatedly jump while already in the air.
The player lands on platforms without falling through them.

Platforms and Collision Detection

The game contains at least three platforms.
The player can stand on the top of each platform.
The player cannot pass through solid platforms from above.
The player respawns or loses when falling below the screen.

Hazards and Collectables

The game includes at least one hazard.
The player loses a life or restarts after touching a hazard.
The game includes at least one collectable item.
The score increases when a collectable is collected.

Level Completion

The level has a clear finish point.
The player wins the level by reaching the finish point.
The game displays a win message when the level is completed.
The game allows the player to restart after winning or losing.

User Interface

The score is visible during the game.
The number of lives or attempts is visible during the game.
The game has a simple start screen or instruction screen.
The controls are explained to the player.

Testing and Evaluation

Each main feature is tested using normal, boundary and error test cases where appropriate.
At least one user tests the game and gives feedback.
The game is improved in response to testing or feedback.
The final evaluation compares the finished game against the original success criteria.

These success criteria give the project structure.

They also give the student a ready-made testing framework.

Turning Success Criteria Into Evidence

A Level projects need evidence of development, not just the final program.

For each success criterion, the student should be able to collect proof.

That proof might include:

screenshots of the game working
code snippets with explanation
test tables
user feedback
before-and-after improvements
notes explaining bugs and fixes
diagrams showing how the game logic works

For example, if the success criterion is:

The player can jump only when standing on a platform.

The evidence might include:

a screenshot of the player standing on a platform
a screenshot of the player jumping
a test showing that pressing jump in mid-air does not create another jump
a code explanation showing how the program checks whether the player is on the ground
a note explaining any bug that occurred during development

This is much stronger than simply saying “jumping works”.

The Main Technical Problems We Expect to Face

It is useful to predict problems before they happen.

This is not being negative. It is good project planning.

A platform game is likely to create problems such as:

the player falling through platforms
the player getting stuck inside platforms
jumping feeling too high or too low
collision detection working from the top but not from the side
the player being able to jump repeatedly in the air
moving platforms causing strange behaviour
the score not resetting properly
levels becoming too easy or too difficult
the game running at different speeds on different computers
sound or graphics taking too much development time

These problems are not reasons to avoid the project.

They are reasons the project is worthwhile.

A project with no problems gives the student very little to discuss. A project with genuine problems and sensible solutions gives the student excellent development evidence.

Deciding the Tools

Students can build this type of game in several ways.

Possible tools include:

Python with Pygame
JavaScript with HTML5 Canvas
Godot
Unity in 2D mode
Java
C# with a simple framework

For an A Level project, the best tool is usually the one the student understands well enough to explain.

That is important.

A student using a powerful game engine without understanding the code may struggle to produce a strong write-up. A student using a simpler environment but explaining the algorithms clearly may produce a better project.

For this series, the ideas will be kept general enough to apply to different languages, but Python with Pygame or JavaScript with Canvas would both be realistic options for many students.

The important point is not the tool. The important point is the thinking.

Designing the First Version of the Game

The first version should be deliberately simple.

A sensible first design might include:

screen size: 800 by 600 pixels
player: simple rectangle or sprite
controls: left arrow, right arrow and space bar
platforms: rectangles stored in a list
gravity: applied each frame
jump: allowed only when standing on a platform
hazard: one red block or spike area
collectable: one coin or star
finish point: one flag or door
score: displayed at the top of the screen

This gives us enough to build a basic level.

A possible first level could be:

the player starts on the ground at the left
there are three platforms at increasing heights
one collectable is placed on a platform
one hazard is placed on the ground
the finish point is placed on the final platform

That is a complete level.

It is small enough to build, but it contains all the core ideas.

A Simple Project Brief

Students often benefit from writing a short project brief.

Here is an example.

I will create a 2D platform game for students aged 11–16 who enjoy simple retro-style games. The player will control a character who must move through a level, jump between platforms, avoid hazards, collect items and reach a finish point. The game will begin with a simple level and may be expanded to include multiple levels, lives, high scores and improved graphics. The project will focus on movement, gravity, collision detection, scoring, testing and user feedback.

This is a good starting brief because it is clear and realistic.

It identifies:

the type of program
the target users
the main features
possible extensions
the programming focus

That is much better than simply saying, “I am going to make a game.”

User Requirements

Even a simple game needs users.

For this project, the likely users might be younger students, friends, classmates or beginner gamers.

Possible user requirements could include:

The game should be easy to understand.
The controls should be simple.
The player should know what the objective is.
The difficulty should increase gradually.
The game should restart easily after losing.
The score should be visible.
The game should not require complicated instructions.
The game should run on a normal school or home computer.

These requirements help shape the design.

For example, if the target user is a younger student, the controls should be simple and the first level should not be too difficult. If the user is another A Level student, the game might include more challenging levels and a high score system.

Avoiding the Common A Level Project Trap

The common trap is trying to make the project impressive too early.

Students sometimes spend days choosing sprites, drawing backgrounds, finding sound effects or planning a storyline before the basic game works.

That is the wrong order.

The first priority is not making the game beautiful.

The first priority is making the game function.

A sensible order is:

Get the window working.
Get the player on the screen.
Add left and right movement.
Add gravity.
Add jumping.
Add platforms.
Add collision detection.
Add a win condition.
Add hazards.
Add scoring.
Add levels.
Improve appearance and sound.

Graphics and sound can come later.

A plain rectangle that moves correctly is better than a beautiful character that falls through the floor.

Planning the First Few Development Stages

The project can be broken into weekly development stages.

Stage 1: Planning and Success Criteria

Define the idea, users, features and success criteria.

Stage 2: Game Window and Player Movement

Create the game window and allow the player to move left and right.

Stage 3: Gravity and Jumping

Add vertical movement, falling and jumping.

Stage 4: Platforms and Collision Detection

Allow the player to land on platforms and prevent falling through them.

Stage 5: Hazards, Collectables and Scoring

Add danger, reward and a visible score.

Stage 6: Level Design

Create a full playable level and possibly a second level.

Stage 7: Menus, Lives and Restarting

Add structure around the game.

Stage 8: Testing and User Feedback

Test features properly and improve the game.

Stage 9: Evaluation and Further Development

Compare the finished game with the success criteria and suggest improvements.

This is a controlled route from idea to working game.

It also gives students a strong structure for their project log.

What Should Be in the Student’s Project Folder From Day One?

A good project folder should not just contain code.

From the beginning, students should collect evidence.

A sensible folder structure might include:

Project Brief
User Requirements
Success Criteria
Design Notes
Algorithms
Development Log
Testing
User Feedback
Screenshots
Final Evaluation
Source Code

This helps avoid the last-minute panic of trying to recreate evidence after the project is finished.

The best evidence is collected while the project is being developed.

Practical Task for Students

Before writing the game, students should complete the following task.

Platform Game Planning Task

Write a one-page plan for your platform game.

Include:

The title of the game.
The target user.
The basic objective.
The controls.
The essential features.
The desirable features.
The extension features.
At least ten clear success criteria.
Three possible technical problems.
How you will collect evidence during development.

This task turns a vague idea into a project.

It also forces students to think realistically before they start coding.

Example Mini Plan

Game Title

Escape the Platforms

Target User

Students aged 11–16 who enjoy simple retro games.

Objective

The player must move across platforms, collect stars, avoid hazards and reach the exit flag.

Controls

Left arrow: move left
Right arrow: move right
Space bar: jump
R key: restart level

Essential Features

player movement
jumping
gravity
platforms
collision detection
hazards
collectables
score
finish point
restart option

Desirable Features

multiple levels
lives
simple sound effects
high score table
moving enemies

Extension Features

level editor
animated sprites
difficulty settings
saved high scores
moving platforms

Example Success Criteria

The player moves left and right using the keyboard.
The player jumps when the space bar is pressed.
The player falls when not supported by a platform.
The player lands on platforms correctly.
The player cannot jump repeatedly while in the air.
The player loses when touching a hazard.
The score increases when a star is collected.
The level ends when the player reaches the flag.
The player can restart the level after losing.
The game displays the score during play.

This is not a complete project, but it is a very good starting point.

Final Thoughts: A Good Game Begins Before the Code

A platform game is an excellent A Level project idea if it is kept under control.

It gives students real programming problems to solve: movement, gravity, jumping, collision detection, level design, scoring and testing.

But it only works as a project if it begins with clear planning.

The student must know what they are building, who it is for, what features are essential and how success will be measured.

The first version does not need polished artwork. It does not need sound effects. It does not need twenty levels.

It needs one thing above all else.

It needs to work.

Once the basic game works, everything else can be improved.

In the next article, we will move from planning to building the first working version: creating the game window, placing the player on the screen and getting simple left and right movement working.

01 July 2026

What Tools Do You Really Need to Learn Maths?

Is a Ruler and Calculator Enough?

When students arrive for maths tuition, they nearly always have two things: a calculator and a ruler. Sometimes they have a pencil. Occasionally they have a compass. Very occasionally they have a full geometry set that still looks as if it has never been opened.

This raises a good question:

What tools do you actually need to learn maths properly?

Is a calculator enough? Does anyone really need a compass anymore? Is a 360-degree protractor worth buying? And what about set squares — are they useful mathematical instruments or just plastic triangles that sit forgotten at the bottom of a school bag?

The answer is that maths is not only about getting the answer. It is also about seeing structure, measuring carefully, drawing accurately and understanding relationships. Good tools do not replace thinking, but they can make thinking much clearer.

The Calculator: Useful, But Not a Substitute for Understanding

The calculator is probably the most-used mathematical tool in school. For GCSE and A Level students, it is essential. It saves time, reduces arithmetic errors and allows students to tackle more advanced problems involving trigonometry, statistics, standard form, logarithms and probability.

But there is a danger.

Some students reach for the calculator before they have understood the question. They type numbers in, press buttons and hope the display gives them something useful. That is not maths. That is button pressing.

A calculator is excellent when a student already knows what they are trying to calculate. It is much less helpful when they do not understand the method.

For example, in trigonometry, the calculator can find:

sin 35°, cos 62° or tan 18°

But it cannot decide whether the problem needs sine, cosine or tangent. That decision comes from understanding the triangle, identifying the sides and choosing the correct relationship.

The same is true in statistics. A calculator may find the mean or standard deviation, but the student still needs to know what the answer means and how to interpret it in context.

The calculator is powerful, but it is not magic. It should support mathematical thinking, not replace it.

The Ruler: More Important Than Students Think

The humble ruler is often underestimated. Students use it to draw straight lines, but many do not use it carefully.

In geometry, graphs, scale drawings and constructions, accuracy matters. A poorly drawn line can make a correct method look wrong. A graph with uneven axes can make a perfectly good answer impossible to read. A triangle drawn carelessly can lead to the wrong conclusion.

A ruler is needed for:

Drawing accurate graphs
Measuring lengths
Constructing scale diagrams
Drawing axes
Producing neat working
Interpreting gradient and intercepts visually

One of the simplest improvements many students can make is to stop sketching everything roughly when accuracy is required. A clean, ruled diagram often helps the brain organise the problem.

In my own teaching, I often find that when a student draws a clear diagram, the problem suddenly becomes much easier. The maths was not impossible; the picture was simply too messy to understand.

The Compass: The Forgotten Tool That Still Matters

Many students think the compass is only for drawing circles. It does draw circles, of course, but that is only part of its value.

A compass is a construction tool. It helps students understand geometry in a much deeper way.

With a compass, students can construct:

Perpendicular bisectors
Angle bisectors
Equilateral triangles
Loci
Arcs
Circles
Accurate geometric diagrams

This matters because construction is not just about making a neat drawing. It shows why certain mathematical facts are true.

For example, when students construct a perpendicular bisector, they can see that every point on that line is the same distance from two fixed points. That is not just a rule to memorise. It becomes visible.

The same applies to loci. Many students find loci difficult because they try to learn them as abstract statements. But when they use a compass to draw points a fixed distance from a point, or from a line, the idea becomes much clearer.

A compass helps turn geometry from a list of facts into something physical and visual.

Do You Really Need a Protractor?

Yes — especially at GCSE level.

Angles appear in geometry, bearings, constructions, scale drawings and trigonometry. Students need to be able to measure and draw them accurately.

A standard 180-degree protractor is enough for many school tasks. However, it does have one common problem: students often read the wrong scale. Most semicircular protractors have two sets of numbers running in opposite directions, and it is surprisingly easy to measure 110° when the correct angle is 70°.

That is where the 360-degree protractor can be useful.

Is a 360-Degree Protractor Worth It?

A 360-degree protractor is not essential for every student, but it can be very helpful.

It is particularly useful for:

Bearings
Full-turn angles
Rotations
Vectors
Navigation-style problems
Polar diagrams
A Level mechanics diagrams
Any situation where angles are measured clockwise from north

Bearings are a classic example. Students often struggle because bearings are measured clockwise from north and always written as three figures, such as 045°, 120° or 275°.

A 360-degree protractor makes this more natural because the full circle is already visible. Instead of flipping the protractor around or trying to imagine the missing half of the circle, the student can see the complete rotation.

For students who find spatial reasoning difficult, that can make a real difference.

Is it absolutely necessary? No.

Is it useful? Yes, especially for students who struggle with bearings and rotations.

What About a Set Square?

The set square is another tool many students ignore. It is not needed every day, but it is useful when drawing accurate perpendicular and parallel lines.

A set square can help with:

Drawing right angles
Constructing perpendicular lines
Drawing parallel lines
Producing accurate diagrams
Technical drawing
Geometry and transformations

In many school maths lessons, students can manage without one. A ruler and protractor can often do the job. But a set square makes certain tasks quicker, cleaner and more accurate.

For students doing design, engineering, physics or technical subjects, set squares become more valuable. They help build the habit of drawing diagrams with precision.

In maths, that habit matters. A right angle that is almost right is not always good enough.

Pencil, Rubber and Sharpener: The Basic Tools Still Matter

It may sound obvious, but students need a pencil.

Graphs, diagrams, constructions and sketches should usually be done in pencil. Maths involves trial, correction and refinement. A pen is fine for written working, but a pencil allows students to adjust drawings and correct mistakes cleanly.

A good rubber matters too. So does a sharpener. Blunt pencils create thick, inaccurate lines, especially when plotting graphs or drawing constructions.

These are small things, but they affect the quality of the work.

A student with a sharp pencil, a ruler and a clear diagram often produces better work than a student with an expensive calculator but messy presentation.

Graph Paper: A Tool for Thinking

Graph paper is not always thought of as a tool, but it is one of the most useful supports in maths.

It helps students understand:

Coordinates
Gradients
Intercepts
Proportion
Transformations
Area
Scale
Functions

At GCSE and A Level, graphs are not just drawings. They are mathematical objects. They show relationships.

A straight-line graph can reveal a gradient. A curve can show a changing rate. A transformation can show how a shape has moved, stretched or reflected.

Graph paper gives structure. It slows students down in a good way and encourages accuracy.

For students who struggle with algebra, graphs can often provide a visual bridge. Seeing the line helps them understand the equation.

Maths Is Not Just Calculation

One of the biggest misconceptions about maths is that it is mostly calculation.

Calculation is important, but maths is also about:

Shape
Space
Pattern
Structure
Measurement
Logic
Representation
Modelling

This is why tools matter. A calculator helps with calculation, but it does not help much with visualising a perpendicular bisector or understanding why bearings work.

A compass, ruler, protractor and set square help students interact with maths physically. They make abstract ideas more concrete.

For some students, this is the difference between memorising a rule and actually understanding it.

Practical Example: Bearings

Consider this common GCSE-style question:

A ship sails 8 km on a bearing of 060°, then 5 km on a bearing of 140°. Draw a scale diagram to find its final distance from the starting point.

A student needs:

A ruler to draw the scale distances
A protractor to measure the bearings
A pencil to draw accurately
Possibly a 360-degree protractor to make the bearings easier
A clear understanding of north lines

A calculator alone is not enough.

In fact, this type of question is a perfect example of why maths tools matter. The student is not simply calculating. They are modelling a journey.

They need to measure, draw, interpret and reason.

Practical Example: Loci

Loci questions often cause confusion.

A typical question might ask:

Shade the region that is less than 4 cm from point A and closer to line AB than line AC.

To solve this, a student may need:

A compass to draw the circle or arc
A ruler to draw straight lines
A protractor or compass construction to create angle bisectors
A pencil to shade the correct region

Again, the calculator has almost no role. The problem is about space and distance, not arithmetic.

Students who have practised using a compass usually find this much easier than those who only try to remember the rule.

Practical Example: Trigonometry Diagrams

Even in calculator-heavy topics such as trigonometry, drawing tools are important.

When solving a triangle problem, students should draw a clear diagram, label the sides and mark the angle. The diagram does not always need to be perfectly to scale, but it does need to be clear enough to show the relationship between the information given.

A neat diagram can help students decide whether to use:

Pythagoras’ theorem
Sine
Cosine
Tangent
The sine rule
The cosine rule

The calculator then finishes the calculation, but the diagram starts the thinking.

The Minimum Maths Toolkit

For most GCSE students, I would recommend:

Scientific calculator
30 cm ruler
Pencil
Rubber
Sharpener
Compass
Protractor
Graph paper or exercise book with squared paper

A 360-degree protractor is a useful extra, particularly for bearings. A set square is helpful but not essential for most students, unless they are doing a lot of technical drawing, design work, geometry or physics diagrams.

For A Level students, the calculator becomes even more important, but the need for clear diagrams does not disappear. In mechanics, vectors, forces, projectiles and moments, a good diagram is often the key to the whole question.

The Tool Is Only Useful If the Student Knows How to Use It

Buying a geometry set is not enough. Students need to practise using it.

Many students own a compass but cannot use it confidently. Some have protractors but measure from the wrong side. Some have calculators but do not know how to change between degrees and radians, or how to use standard form correctly.

Tools need practice.

A good lesson is not simply “bring a compass”. It is:

How do we use the compass accurately?
Why does this construction work?
What does this diagram show?
How do we check whether the answer is sensible?

The tool is the start. Understanding is the aim.

Personal Reflection: The Best Tool Is Often the One That Makes the Student Slow Down

In lessons, I often find that the most useful tools are not the most expensive ones. A calculator can be impressive, but sometimes the real breakthrough comes from a pencil, a ruler and a properly drawn diagram.

When a student slows down enough to draw the triangle, mark the angle, measure the bearing or construct the locus, they often stop guessing. They begin to see the problem.

That is the real value of mathematical tools.

They encourage care. They encourage precision. They encourage thinking.

And in maths, those habits matter just as much as the final answer.

Conclusion: A Calculator Is Not Enough

So, is a ruler and calculator enough?

For some topics, perhaps. For learning maths properly, no.

A calculator helps with arithmetic and functions. A ruler helps with accuracy. A compass reveals geometry. A protractor makes angles measurable. A 360-degree protractor can make bearings and rotations clearer. A set square helps with perpendicular and parallel lines.

None of these tools will do the maths for the student. But they can help the student see the maths more clearly.

Maths is not just about pressing buttons. It is about understanding relationships, recognising patterns and representing ideas accurately.

Sometimes the right tool does not just help you draw the answer.

It helps you understand the question.

30 June 2026

Archimedes’ Principle: The Simple Floating Beaker Experiment That Makes Upthrust Visible

Some physics experiments are impressive because they use expensive equipment, flashing sensors or complicated data logging. Others are powerful because they are wonderfully simple.

Archimedes’ Principle is one of those ideas that can feel abstract when written as a sentence in a textbook:

The upthrust on an object in a fluid is equal to the weight of the fluid displaced.

Students often learn the words. They may even be able to quote the definition in an exam. But do they really understand what it means?

That is where a large measuring cylinder, some water, and a small floating beaker can do something remarkable. They can make upthrust visible.

The Experiment: A Beaker Floating Inside a Measuring Cylinder

The setup is very simple.

Take a large measuring cylinder or tall transparent container and partly fill it with water. Then place a small empty beaker, plastic cup, or weighing boat into the water so that it floats.

At first, the beaker floats high in the water. Only a small part of it is submerged because the beaker is light. It does not need to displace much water to support its own weight.

Now slowly add water into the floating beaker.

The beaker sinks lower and lower.

It is not sinking because it is “failing” to float. It is still floating. It is simply becoming heavier, so it must displace more water to produce a larger upthrust.

This is the key point.

A floating object adjusts how much water it displaces until the upthrust equals its weight.

The Important Detail: Where the Added Water Comes From

There is one subtle but important teaching point here.

If you add water to the floating beaker from outside the measuring cylinder, then you have added extra water to the whole system. The water level in the measuring cylinder will rise.

However, if the water poured into the floating beaker is taken from the surrounding water in the same measuring cylinder, the overall water level remains the same.

This is the clever part.

The water has simply been moved from outside the beaker to inside the beaker. The floating beaker now displaces extra water equal to the weight of the water placed inside it. That extra displacement balances the volume of water removed from the surrounding cylinder.

So the beaker floats lower, but the water level does not change.

To many students, this feels surprising at first. It looks as though the beaker should make the water rise as it sinks lower. But Archimedes’ Principle explains exactly why it does not.

What Is Upthrust?

Upthrust is the upward force exerted by a fluid on an object.

When an object is placed in water, it pushes water out of the way. The water pushes back. This upward push is upthrust.

For a floating object:

Upthrust = weight of the object

For Archimedes’ Principle:

Upthrust = weight of fluid displaced

So for a floating beaker:

Weight of beaker + weight of water inside it = weight of water displaced

The beaker sinks lower until enough water has been displaced to balance the total weight.

This is why a small empty boat floats high, but a heavily loaded boat floats lower. It is also why there is a load line painted on ships. The ship is allowed to sit lower when carrying cargo, but only up to a safe limit.

Why This Experiment Works So Well for A Level Physics

At A Level, students are expected to move beyond simply saying “things float because they are less dense than water.”

That explanation is often incomplete.

A steel ship floats, but steel is denser than water. A hollow metal can may float, but a solid piece of the same metal may sink. A plastic beaker floats differently depending on whether it is empty or full.

The real explanation involves forces, density, displaced volume and equilibrium.

This simple experiment allows students to see:

An object floating in equilibrium
Weight acting downwards
Upthrust acting upwards
Greater weight requiring greater displacement
The connection between volume displaced and force
Why floating objects sit lower when loaded

It also shows why physics is not just a collection of equations. The equation describes something real that can be observed on the bench.

A Simple Calculation to Support the Demonstration

Suppose the empty beaker has a mass of 50 g.

Its weight is approximately:

0.05 kg × 9.8 N/kg = 0.49 N

To float, it must displace water weighing 0.49 N.

Since water has a density of about 1000 kg/m³, the beaker needs to displace about 50 cm³ of water.

Now add 100 g of water to the beaker.

The total mass becomes:

50 g + 100 g = 150 g

The total weight is now approximately:

0.15 kg × 9.8 N/kg = 1.47 N

The beaker must now displace about 150 cm³ of water.

So it floats lower.

The beaker has not become “less floaty.” It has simply become heavier and therefore needs to displace more water to remain in equilibrium.

The Bucket and Pail Version

Another classic version of this experiment is the bucket and pail demonstration.

An object is lowered into water and the displaced water is collected in a small pail or overflow can. The weight of the displaced water can then be compared with the upthrust on the object.

This version is excellent because it makes the phrase “weight of water displaced” feel more physical. The displaced water can be collected, measured and weighed.

The bucket and pail method is particularly useful when teaching students who need to connect the idea of upthrust with practical measurement. It also links naturally to required practical skills: accurate measurement, uncertainty, repeats and experimental design.

However, the floating beaker version has a different advantage. It is extremely visual. Students can see the beaker sinking lower as more water is placed inside it. There is no need for a complex apparatus. The physics is right there in front of them.

Common Misconceptions This Demonstration Helps Fix

One of the most common misconceptions is that floating depends only on density.

Density is important, but it is not the whole story. Shape and displaced volume matter. A lump of metal may sink, but a metal boat can float because it encloses air and displaces a large volume of water.

Another misconception is that the upthrust is always equal to the weight of the object. That is only true when the object is floating or stationary in equilibrium. If an object is sinking, the weight is greater than the upthrust. If it is rising, the upthrust is greater than the weight.

A third misconception is that objects float “because water pushes them up.” That is partly true, but students need to go further. They need to explain how the size of that upward force is determined.

Archimedes’ Principle gives the complete explanation.

Bringing It Back to Real Life

This experiment is not just about a beaker in a measuring cylinder. It explains some very real situations.

It explains why a rowing boat sits lower when more people climb into it.

It explains why cargo ships have load lines.

It explains why a submarine can rise or sink by changing the amount of water in its ballast tanks.

It explains why life jackets work by increasing the volume of water displaced without adding much weight.

It explains why a person may float more easily in seawater than freshwater, because seawater is denser and provides a greater upthrust for the same displaced volume.

These real-world examples help students see that Archimedes’ Principle is not an isolated classroom trick. It is one of the key ideas behind floating, sinking, ship design, submarines, hydrometers and even swimming.

A Personal Reflection: Simple Experiments Often Teach Best

I have always liked experiments like this because they remind students that physics does not always need to begin with algebra.

Sometimes it begins with noticing something odd.

A beaker floats. Add water and it floats lower. Take the added water from the surrounding container and the level stays the same. That is a puzzle.

Once students have seen the puzzle, the equation has a reason to exist.

This is especially important at A Level. Students can become very good at rearranging equations while still not fully understanding the physical situation. A simple demonstration forces them to ask what is actually happening.

The best practical work is not always the most complicated. Sometimes the most effective lesson comes from a beaker, a cylinder and a question:

Why did the water level not change?

Teaching Extension: Turning It Into an A Level Discussion

For stronger students, this experiment can be extended into a deeper discussion.

Ask them to predict what will happen before the water is added. Then ask them to explain the result using forces. Then ask them to explain it using density and displaced volume. Finally, ask them to write a short exam-style answer using correct scientific language.

A good answer might include:

As water is added to the floating beaker, the total weight of the beaker increases. The beaker therefore sinks lower into the water so that it displaces a greater volume of water. The increased volume of displaced water produces a larger upthrust. When floating in equilibrium, the upthrust is equal to the total weight of the beaker and the water inside it.

That is exactly the kind of explanation examiners want: clear, precise and linked to the correct principle.

Conclusion: Archimedes Made Visible

Archimedes’ Principle is one of the great ideas in physics because it connects forces, fluids, density and equilibrium in one elegant statement.

But for students, it can remain just a phrase unless they see it happen.

The floating beaker experiment makes the principle visible. The beaker sinks lower as it becomes heavier. It displaces more water. The upthrust increases. The object continues to float when the forces are balanced.

It is simple, visual and memorable.

And sometimes that is exactly what good physics teaching needs.

29 June 2026

Killer Plants in the Classroom: What Sundews, Venus Flytraps and Pitcher Plants Teach Us About Evolution

There are some plants that immediately catch a student’s imagination. A daffodil is useful. A geranium is familiar. A broad bean seedling is good for showing growth. But put a Venus flytrap, a sundew or a pitcher plant on the bench and suddenly the whole room changes.

Students lean forward.

They ask questions.

“Does it really eat flies?”

“Can it bite you?”

“Why would a plant need to catch insects?”

That is the magic of carnivorous plants. They look like something from science fiction, but they are real, living examples of evolution, adaptation, plant physiology and ecology. They are not just curiosities. They are excellent teaching tools.

Plants That Break the Rules — Or Seem To

Most students learn early on that plants make their own food by photosynthesis. They use light energy, carbon dioxide and water to make glucose. So the idea of a plant “eating” an insect feels wrong.

But carnivorous plants are not eating insects in quite the same way that animals eat food.

They still photosynthesise. They are still plants. They still need light. What they are short of is not usually energy, but nutrients, particularly nitrogen and minerals. Many carnivorous plants grow in bogs, wetlands or poor acidic soils where ordinary plants struggle to obtain enough nutrients from the ground.

So evolution has found a different route.

Instead of relying only on the soil, these plants have developed specialised leaves that trap and digest small animals, usually insects. The insect becomes a nutrient supplement.

In teaching terms, this is a perfect moment. Students already know that plants need minerals. They already know that animals contain protein. Now they can connect the two ideas and see why a plant might benefit from catching prey.

Evolution in Action

Carnivorous plants are a wonderful example of adaptation.

They did not suddenly decide to become insect-eaters. Evolution does not work like that. Instead, small variations that helped certain plants survive in poor conditions were favoured over many generations.

A slightly stickier leaf might trap more insects.

A deeper leaf might hold rainwater and drowned insects.

A leaf with more digestive enzymes might gain more nutrients.

A plant that gained nutrients from trapped insects could survive better, grow stronger and produce more seeds. Over time, these small advantages could produce very unusual structures.

The Venus flytrap did not need to know what it was doing. Natural selection did the work.

This helps students move beyond the simplistic idea that animals or plants “try” to evolve. Evolution is not about effort. It is about variation, selection and inheritance.

The Sundew: A Sticky Trap

The sundew is one of the most beautiful carnivorous plants to show students.

Its leaves are covered in tiny red or green tentacles, each tipped with a glistening droplet. The droplets look like dew, which is where the plant gets its name. But this “dew” is sticky mucilage.

To an insect, it may look like a tempting source of moisture or nectar. Once it lands, it becomes trapped.

The more the insect struggles, the more contact it makes with the sticky hairs. Some sundew leaves slowly curl around the prey, increasing the surface area in contact with the insect. Digestive enzymes then help break down the prey and release nutrients.

This is a good opportunity to discuss:

adaptation
specialised plant cells
enzymes
surface area
slow plant movement
the difference between energy and nutrients

Students are often surprised by the movement. They think of plants as passive and still. Sundews challenge that assumption.

The Venus Flytrap: A Plant That Counts

The Venus flytrap is probably the most famous carnivorous plant of all.

Its trap is a modified leaf with two lobes. Inside are sensitive trigger hairs. When an insect touches these hairs in the right sequence, the trap snaps shut.

This is where the biology becomes especially interesting. The plant must avoid wasting energy by closing for every raindrop, piece of dust or accidental touch. It therefore responds to repeated stimulation rather than a single random event.

In simple classroom language, the plant is not “thinking”, but it is responding to stimuli.

This makes the Venus flytrap a superb link between plant biology and nervous-system-style ideas. Students can compare it with reflexes, electrical signals and stimulus-response pathways, while remembering that plants do not have brains.

The Venus flytrap also raises excellent questions:

Why must the trap close quickly?
Why does the plant need trigger hairs?
Why might repeated stimulation be useful?
Why does the trap not close every time something touches it?
What would happen if the trap closed too often?

These questions are much better than simply saying, “It catches flies.”

Pitcher Plants: The Pitfall Trap

Pitcher plants use a very different method.

Instead of snapping shut or sticking prey to their leaves, they form deep tube-like or jug-like structures. These are also modified leaves. The insect is attracted by colour, smell or nectar. It lands on the rim, slips on the smooth surface, falls into the liquid below and cannot easily escape.

The plant then digests the prey and absorbs the nutrients.

Pitcher plants are excellent for teaching structure and function. Every part of the trap has a job:

the bright colour attracts prey
the rim encourages insects to land
the slippery surface makes escape difficult
the deep tube holds fluid
the digestive liquid breaks down the prey
the plant absorbs the released nutrients

Students can draw and label a pitcher plant very effectively. It becomes a biological machine, but one produced by evolution rather than engineering.

A Practical Classroom Question: Are They Animals or Plants?

One of the most useful discussions begins with a deliberately simple question:

“If a plant eats insects, is it still a plant?”

Students quickly realise that the answer is yes.

Carnivorous plants still contain chlorophyll. They still photosynthesise. They still have roots, stems, leaves and flowers. Their prey gives them extra nutrients, not their main source of energy.

This helps students correct a common misunderstanding. Plants do not absorb “food” from the soil in the same way animals eat food. Plants make glucose using photosynthesis, but they need mineral ions for healthy growth.

Carnivorous plants make this distinction memorable.

How to Look After Carnivorous Plants

Carnivorous plants are fascinating, but they are also easy to kill if treated like ordinary houseplants.

The most common mistake is kindness.

People feed them fertiliser. They use normal compost. They water them with tap water. They poke the traps to make them close.

All of these can damage the plant.

Most carnivorous plants need conditions that imitate their natural habitat. That usually means:

bright light
moist conditions
low-nutrient growing medium
rainwater, distilled water or reverse-osmosis water
no ordinary fertiliser
no rich compost
no constant handling of the traps

For students, this is a useful ecological lesson. An organism is adapted to a particular environment. Change the environment too much and the adaptation becomes a problem.

A Venus flytrap adapted to poor soil is not helped by rich compost. A bog plant is not helped by being kept dry. A plant adapted to clean rainwater may struggle with mineral-rich tap water.

Looking after the plant becomes a practical study in ecology.

A Simple Student Investigation

Carnivorous plants can lead into small, careful investigations. These do not need to involve harming the plant.

Students could investigate:

how different carnivorous plants trap prey
how the structure of each trap matches its function
why low-nutrient soil encourages carnivory
how light affects plant growth
how water type affects long-term health
how a Venus flytrap avoids closing unnecessarily
how sundew tentacles respond over time

A good classroom task is to compare three trap types:

Sundew — sticky trap
Venus flytrap — snap trap
Pitcher plant — pitfall trap

Students can then answer:

What attracts the insect?
What prevents escape?
How is the prey digested?
What nutrients does the plant gain?
What is the evolutionary advantage?

This gives a clear structure and helps students move from fascination to scientific explanation.

Why Students Remember Them

I have found that students remember unusual examples.

They may forget a diagram of a typical leaf. They may forget a list of mineral deficiencies. But they remember the plant that catches flies.

That memory gives the teacher something to build on.

When teaching adaptation, I can return to the Venus flytrap.

When teaching enzymes, I can return to digestion in pitcher plants.

When teaching mineral ions, I can ask why a plant would need nutrients from insects.

When teaching ecology, I can talk about bogs, wetlands and poor soils.

Carnivorous plants become a hook. They make abstract ideas visible.

The Bigger Lesson: Life Finds a Way

What makes carnivorous plants so powerful as a teaching example is that they show how flexible life can be.

A plant is rooted in one place. It cannot chase prey. It cannot hunt like a spider or a bird. Yet evolution has produced leaves that snap, leaves that stick, and leaves that form deadly cups of digestive fluid.

That is extraordinary.

It also reminds students that evolution is not about progress towards a perfect form. It is about survival in a particular environment. A cactus, an orchid, a nettle and a Venus flytrap are all successful in different ways.

The question is not “Which plant is best?”

The question is “Best for what environment?”

Conclusion: The Perfect Plant for Curious Minds

Carnivorous plants are more than classroom novelties. They are living examples of evolution, adaptation, ecology, enzymes, plant nutrition and stimulus response.

They fascinate students because they appear to break the rules. But once we study them carefully, they actually help students understand the rules more deeply.

The sundew shows us patience and stickiness.

The Venus flytrap shows us rapid response and energy-saving precision.

The pitcher plant shows us structure, attraction and entrapment.

Together, they show us that plants are far more active, complex and surprising than many students first imagine.

And perhaps that is the best reason to teach them.

A good science lesson should not just answer questions. It should create better ones.