🔁 Lesson 2.2: Loops — Making Things Repeat
Why write a block ten times when you can tell Scratch "do this ten times"? Loops are the first idea that makes kids feel like real programmers — and they're the secret behind every animation and game.
🎯 Learning Objectives
- Use the repeat and forever loops
- Understand what goes inside a loop vs. outside it
- Build a smooth walking animation with a loop
- Recognize and fix a runaway "forever" loop
Estimated Time: 35 minutes • Builds on: Sequences (2.1)
In This Lesson
🎓 Learn It: Why loops exist
Imagine you want the cat to take 20 little steps. You could drag in 20 "move" blocks. Painful — and if you wanted 21, you'd start over. A loop says "do this again and again" so one block replaces twenty.
😩 The hard way
…and 16 more. No thanks.
😎 The loop way
One loop. Change 20 to 100 in a heartbeat.
Loops live in the orange Control category. Notice they're C-shaped — blocks you place inside the "mouth" of the C get repeated.
🎓 Learn It: repeat vs. forever
| Loop | What it does | Use it when… |
|---|---|---|
| repeat 10 | Runs the inside blocks a set number of times, then moves on | You know how many times (blink 3 times, take 20 steps) |
| forever | Runs the inside blocks endlessly until you press stop | Something should always be happening (a heartbeat, constant fall, always checking a key) |
⚠️ "forever" never ends on its own
Any block placed after a forever loop will never run — the program never gets past it. That's not a bug in Scratch; it's the loop doing its job. Use the red stop to end it.
🎓 Learn It: What goes inside the loop
This is the idea kids (and adults!) trip on: only the blocks inside the C repeat. Compare:
Say is inside → repeats
"Ha!" three times.
Say is outside → runs once
Moves 3×, then says "Done!" once.
🛠️ Try It: A real walking cat
In Module 1 the cat "jumped" across. With a loop we get smooth walking. The cat has two costumes; alternating them while moving looks like real steps.
- Start with when 🟩 clicked, then go to x: -200 y: 0 (start at the left).
- Add a repeat 20 loop (Control).
- Inside the loop, add: move 20 steps, next costume, and wait 0.1 seconds.
Press the green flag: the cat strides across the stage, legs moving. That's your first animation! The wait 0.1 sets the walk speed — smaller is faster.
💡 Challenge: make it pace back and forth forever
Wrap the whole walk in a forever loop and add if on edge, bounce (Motion) plus set the sprite's rotation style to "left-right" so it flips instead of going upside-down. Now it patrols endlessly until you hit stop.
💬 Teach It: Loops all around us
Loops are everywhere in daily life — naming them together makes the abstract idea stick.
Spot-the-loop game
"Brushing teeth is a loop: scrub, scrub, scrub — repeat until clean! Can you think of another loop? What about the wheels on the car, or a song's chorus?"
- Stirring a pot • jumping jacks • a ticking clock • steps while walking • a chorus repeating.
The powerful question
When your child copy-pastes the same block many times, don't correct — ask:
"That works! Is there a block that could do all of those for us at once, so we don't have to make so many?"
Letting them discover the loop is far stickier than telling them.
👧 Ages 5–7
Stick to repeat with small numbers they can count out loud. "Repeat 3 — let's count the jumps!"
🧒 Ages 8–11
Great age for the walking project. Let them tune the wait number and feel how it changes speed.
🧑 Ages 12+
Introduce a loop inside a loop (nesting). E.g., repeat 4 { repeat 10 { move; wait } turn 90 } to trace a square.
⚠️ Common kid bug
They drop a block below the loop expecting it to repeat, or they trap the whole program in a forever so a later block "does nothing." Point at the C-shape: "Is your block inside the mouth, or outside?"
🎯 Quick Check
Question 1: You want the cat to blink exactly 5 times. Best loop?
Question 2: Only which blocks repeat in a loop?
Question 3: A block placed after a "forever" loop will…
Summary & What's Next
🎉 Key Takeaways
- repeat runs a set number of times; forever runs until you press stop.
- Loops are C-shaped — only the blocks inside repeat.
- Alternating costumes inside a loop creates smooth animation.
- Let kids discover loops by asking "could one block do all these?"
🚀 Next up
So far the cat does what we plan. In Lesson 2.3 it starts making decisions — reacting to key presses and touches with if/then and sensing blocks. This is where projects become interactive.