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Computer Programming with Scratch
Week 2: Conditionals & Control Flow
Day 10: Loops + Conditionals

Day 10: Loops + Conditionals

Friday, March 27th, 2026

Objectives

  • I can use a forever loop with if blocks inside it to respond to game events.
  • I can explain why if blocks are often placed inside forever loops in games.
  • I can build a Scratch program that combines loops and conditionals.

Warmup: Which Block Do I Need?

This week you learned two powerful tools:

  • Conditionals (if blocks) — do something only when a condition is true
  • Loops (forever, repeat # times) — do something over and over

For each scenario below, call out which block you would use — forever, repeat # times, or if:

Answer these questions in your head.
Scenarioforeverrepeat # timesif
Draw a square (move and turn 4 times)
Keep checking if the player is touching a wall
Do something only when the score reaches 10
Bounce a sprite off the edge for the whole game
Repeat a dance move 8 times

On Day 8 you drew this flow diagram and wrote pseudocode for it:

    %%{init: {'themeVariables': {'fontSize': '2rem'}}}%%
flowchart LR
    A([Start]) --> B{Is the sprite touching a coin?}
    B -- Yes --> C[Add 1 to score]
    C --> D{Is score = 10?}
    D -- Yes --> E[Say You win!]
    D -- No --> B
    B -- No --> B
    E --> F([Done])

Today we build it.

Checkpoint: Warmup

  • I can tell the difference between a loop and a conditional.
  • I understand that in this diagram, the arrows that loop back mean the code runs over and over.

Work Session: The Game Loop

Most games use the same pattern: a forever loop with if blocks inside it. The loop keeps the game running every frame, and the if blocks check whether something important happened.

Here’s what that looks like in Scratch:

when green flag clicked
forever
if <touching [Coin v]?> then
change [score v] by (1)
end
if <touching [edge v]?> then
say [Ouch!] for (1) seconds
go to x: (0) y: (0)
end
end

Why does the forever loop matter? Without it, each if block would only run once when the green flag is clicked — then stop. The forever loop makes Scratch check those conditions every frame while the game is running.

Build Your Own

Starting from a blank Scratch project, build a program that has all four of the following:

  1. A sprite the player can move using arrow keys or WASD
You’ll have to make the movement code yourself. Look at an earlier project if you forgot how.
  1. A coin or something else collectable that increases the score when touched

When the player touches the coin, you can use the change [score v] by (1) block to increase the score variable.

Then you can use the go to [random position v] block to move the coin somewhere else on the stage.

  1. A forever loop that contains at least two if blocks responding to different events
You can use the example code above as a starting point.
  1. A score variable that increases when a condition is met
To add a variable, go to the Variables category and click Make a Variable. Name it score.

Some ideas for your two conditions:

  • Touching a coin sprite → add 1 to score
  • Touching a wall color → reset position
  • Score reaching 10 → say “You win!” and stop

Checkpoint: Work Session

  • My project has a forever loop.
  • My forever loop contains at least two if blocks.
  • My score variable changes when a condition is met.

Closing: Show and Tell

A few volunteers will share their projects. Hit the Share button in Scratch. Mr. Willingham will add your project to a Studio Page so other students can see it.

Some questions to think about as you play someone else’s project:

  • Where is the forever loop?
  • What conditions are inside it?
  • What happens when each condition is true?

Key takeaway: Almost every game you’ve ever played — Mario, Minecraft, anything — runs on this exact pattern. A loop that never stops, checking conditions every single frame. You just built that.

Useful Blocks 

when green flag clicked

forever
end

if <> then
end

set [score v] to (0)

change [score v] by (1)

if <(score) = (10)> then
say [You win!] for (2) seconds
stop [all v]
end
if <key [right arrow v] pressed?> then
change x by (10)
end

change y by (10)

go to (random position v)

go to x: (0) y: (0)

hide

show

if <touching [Coin v]?> then
change [score v] by (1)
end

Standards

  • MS-CS-FCP.3.2 — Develop a working vocabulary of computational thinking including sequences, algorithms, and iteration (loops).
  • MS-CS-FCP.4.1 — Develop a working vocabulary of programming including coding, debugging, variables, loops, conditionals, and events.
  • MS-CS-FCP.4.5 — Implement a simple algorithm in a computer program.
  • MS-CS-FCP.4.8 — Create a computer program that implements a loop.
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Day 9: Loops