Instructor Notes — Week 7

Theme: Functions, Inputs & Game Logic
Focus Concept: Creating and Reusing Functions
Mini-Projects: Function Challenges (Part A) → Mini Space Invaders (Part B)

Learning Objectives

Participants understand that a function is a small helper program that performs one clear job and can be called when needed.
Participants can create, call, and reuse functions to simplify their code.
Participants explore parameters and return values through guided pseudocode.
Participants apply loops, conditions, and variables to manage behaviour in a game.
Participants connect code structure to maths (timing & repetition) and science (motion & acceleration).

Recap (≈10 min)

Write on the board:

A function is a named helper that “does one job”.
We call it whenever we need that job done.

Prompt discussion:
When might we reuse a helper? (e.g. showing a message, flashing an icon, playing a short sound)

Part A — Function Challenges (≈35 min)

Step 1 — Simple Function (No Inputs)

define function flashHeart
    show icon "heart"
    pause 200 ms
    show icon "small heart"
    pause 200 ms
end function

on start
    flashHeart()
    flashHeart()

Instructor tips

Emphasise definition vs call.
Changing the pause changes rhythm → introduce iteration timing (ms).
Ask: Why use a function instead of copying these lines?

Step 2 — Function with Parameter (Input)

define function flash(times)
    repeat times times
        show icon "heart"
        pause 200 ms
        clear screen
        pause 200 ms
    end repeat
end function

on button A pressed → flash(3)
on button B pressed → flash(1)

Discuss

The word inside brackets is the parameter.
Same recipe, but flexible — the parameter changes how many times it runs.
Try 0, 3, 5 → predict then test.

Step 3 — Function with Return Value (Computation)

define function addNumbers(a, b)
    return a + b
end function

on start
    set total = addNumbers(3, 2)
    show number total

Instructor tips

The function calculates and returns a value to the main program.
Demonstrate that addNumbers(3, 2) produces 5.
Challenge: show number addNumbers(2, addNumbers(1, 1)).

Step 4 — Combining Functions

Encourage chaining simple helpers:

showMessage() + playTone() = an alert system.
flash(times) inside a “game over” function.

💡 Functions are like tools — each one solves a small problem; together they build something complex.

Step 5 — Mini-Challenges (≈5 min)

Create showLevel(level) → display “L” + level and play a tone.
Add a sound when a function finishes.
Modify flash(times) to limit it to a maximum of 5 flashes.
Build a combo function that calls two others in sequence.

Part B — Mini Space Invaders (≈45 min)

Step 1 — Sprites & Setup

create Ship at (2, 4)
create Alien at (0, 0)
make variables: Laser, Bomb
set score = 0

Same 5×5 grid — player bottom, threat top.

Step 2 — Alien Movement (Forever)

forever
    move Alien right 1
    pause 200 ms
    if Alien hits edge → bounce
end

Step 3 — Ship Control (Tilt)

if accel X > 100 → Ship x = Ship x + 1
if accel X < -100 → Ship x = Ship x - 1
(clamp Ship x between 0 and 4)

Science link: Accelerometer detects gravity/tilt → motion input.

Step 4 — Fire a Laser (Button B)

when button B pressed
    create Laser at (Ship x, Ship y)
    repeat 5 times
        pause 100 ms
        move Laser up 1
        if Laser touching Alien
            delete Alien
            increase score by 1
            create Alien at (random x 0..4, y 0)
        end if
    end repeat
    delete Laser

Grid height = 5 rows → five steps to the top.

Step 5 — Alien Drops a Bomb (Forever)

forever
    if Alien x == Ship x
        create Bomb at (Alien x, 0)
        repeat 5 times
            pause 200 ms
            move Bomb down 1
        end repeat
        if Bomb touching Ship → game over
        delete Bomb
end

Symmetry with the Laser but moving downward.

Step 6 — Extensions (if time)

Add a lives variable (start 3; −1 on hit; Game Over at 0).
Add sound effects for laser and hit.
Increase alien speed every 5 points (reduce pause or add levels).
Create a function that shows “Level Up!” or “Wave Cleared!” messages.

Vocabulary Focus

Differentiation

Beginners: follow the guided function build and core controls.
Confident: add parameters, random spawns, and sound effects.
Stretch: build functions with return values or multiple calls per loop.

Assessment & Reflection

Can participants explain what a function is and where they used one?
Can they describe how loops and calls work together?
Can they show how variables store values between functions?
Can they discuss speed (pause) and difficulty in the game?
Observe teamwork, debugging strategies, and safe device handling.

Common Mistakes

Calling a function before it’s defined.
Forgetting to return a value in math functions.
Deleting sprites before checking collisions.
Using coordinates outside 0–4 → sprites “vanish”.

Materials & Setup

BBC micro:bits + USB cables (or simulator)
Chromebooks/laptops with internet access
Optional speakers/headphones for sound effects

Safety & Safeguarding

Keep cables tidy; drinks away from devices.
Sensible volume for sounds.
Encourage turn-taking and pair programming.

Cross-Curricular Links

KS2 Computing Curriculum Mapping

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