Session 17 — Levels & Challenge

Duration: 60 min · Format: live online

What you'll learn: by the end, you can use if/then decisions, detect collisions with the "touching" block, and give a game real win and lose conditions.

Soft skill focus — Resilience

Today you'll also grow Resilience. Building win and lose conditions means things break first — a runaway score, a message that never shows — and makers keep going until it works.

Try this: when your score explodes or your "You Win!" never appears, tell yourself "that's a bug every game-maker hits" — then try one fix at a time (add the respawn line, then re-test) instead of giving up or starting over.

Think about: What broke in your game today, and how did you keep going until you fixed it?

What you'll need

• Open Scratch and click Create — or open your Session 16 project so you can extend it.
• An idea to aim for: the "catch" game from Session 16, upgraded so that when the basket touches the apple the score goes up, and if the apple touches the floor you lose a life.

Hook

Think about these questions:

• How does a game know when you caught the coin, or fell in the pit?
• What makes a game feel too easy or too hard?
• How does the screen decide to show "You Win!" or "Game Over"?

Here's the big idea: today your game learns to make decisions. It will check "is this touching that?" and then choose what to do — score, lose a life, win, or end.

Teach — If/then makes decisions

Here's how decisions work:

• An if / then block (Control) is a decision: if something is true, then do these blocks. If it's not true, it skips them.
• The diamond-shaped slot at the top holds a question that is true or false — for example, "is the apple touching the basket?"

Build this in Scratch:

• Build if <touching [Basket]?> then → change [Score] by 1. Drop it inside a forever loop so the game keeps checking.
• Run it and drag the apple onto the basket — the score jumps. The loop asks the question many times a second; when the answer becomes true, the then blocks run.

⚠ Watch for a runaway score: because the loop checks constantly, one touch can add hundreds of points. Fix it by adding, right after scoring, a reset — go to x: 0 y: 150 (send the apple back to the top) so it's no longer touching.

Quick question: the diamond slot needs a question that is true or false. Is "the apple" a good fit for it? What about "the apple is touching the basket"? (Answer: the second — it can be true or false.)

Teach — Touching, collisions, win & lose

The touching [ ]? block (Sensing) is how a game notices collisions — two things bumping into each other. It's the heart of catching, hitting, and dodging.

Picture the collision logic: if touching the wall, react; otherwise keep moving.

Build this in Scratch:

• Scoring collision: in the apple's forever loop, add if <touching [Basket]?> then → change [Score] by 1, play sound [Pop], go to x: (pick random -200 to 200) y: 150 (respawn somewhere new).
• Losing collision: add if <touching [floor]?> then → change [Lives] by -1 and reset the apple to the top. (Use a floor sprite or check if y < -150.)
• Lose condition: somewhere in a loop, add if <Lives = 0> then → broadcast [game over] → stop [all]. Add a sprite with when I receive [game over] → say [Game Over!].
• Win condition: add if <Score = 10> then → broadcast [you win] → stop [all], with a sprite that says "You Win!"

Now try making it harder (levels):

• A game gets harder by speeding up or adding more. Change change y by -5 so the -5 is a variable Speed, and change [Speed] by -1 every 10 points so falling gets faster.

Key idea: if/then + touching lets a game react — that's what turns moving sprites into a real, winnable, losable game.

Try it: to make the game harder, should the apple fall faster or slower? What block changes that? (Answer: faster; change the change y by number to a bigger negative.)

Activity

Now upgrade your catch game.

Build this, step by step:

1. On the falling sprite: wrap the fall in forever → change y by -5.
2. Inside the loop, add if <touching [your catcher sprite]?> then → change [Score] by 1, play sound [Pop], go to x: (pick random -200 to 200) y: 150.
3. Add if <y < -150> then → change [Lives] by -1 → go to x: (pick random -200 to 200) y: 150 (missed it — reset).
4. Make sure Lives starts at 3 and Score starts at 0 on the green flag.
5. Add a lose check: if <Lives = 0> then → broadcast [game over] → stop [all].
6. Add a win check: if <Score = 10> then → broadcast [you win] → stop [all].
7. Add a sprite that shows "Game Over!" on when I receive [game over] and "You Win!" on when I receive [you win].
8. Test: catch apples to win, miss three to lose.

If something's not working, check:

• Scores that shoot up by hundreds — the caught sprite isn't resetting, so it stays touching. Add the respawn line.
• The if/then is outside a loop, so it only checks once — move it inside the forever loop.
• Win/lose messages that never show — check the broadcast and when I receive names match, and that stop all isn't stopping the message sprite before it can say anything (put the say before stop all if needed).

Tip: change the win score or starting lives to tune how hard your game feels.

Check yourself

Try these — answers are after the arrow.

1. What does an if/then block do? → It checks a true-or-false question; if it's true, it runs the blocks inside; if not, it skips them.
2. Which block lets a game notice two sprites bumping into each other? → The touching [ ]? block (Sensing) — it detects a collision.
3. How could you make a "You Win!" message appear when the score reaches 10? → if <Score = 10> then → broadcast [you win]; a sprite with when I receive [you win] says "You Win!".

Wrap-up

• In your own words, describe one win condition and one lose condition in your game.
• Try this at home — Tune the Challenge: change one thing to adjust the difficulty — the falling speed, the number of lives, or the score needed to win — and decide whether it made the game better. Bring it to Session 18.

Tips & extra challenges

• Watch out: it's easy to think "if/then only runs once when I click it." Alone it checks a single time; games put if/then inside a forever loop so the question is asked continuously. Try both so you feel the difference.
• Want more? Try this: add a second level — when Score reaches 5, broadcast [level 2], switch the backdrop, speed up the falling sprite, and maybe add a second falling object to dodge. Challenge: add an enemy you must avoid: if <touching [enemy]?> then change [Lives] by -1. This is real level design in miniature.

Vocabulary

Resources

• Scratch — free, in your browser, no install (main tool).
• Scratch Wiki: If ... Then — friendly reference on decisions.
• Scratch Wiki: Touching — how collision detection works.
• Scratch Ideas page — starter guides for catch, maze, and dodge games.

Practice set

Practise on your own. Answers are after the arrow.

1. Make the score go up only when the falling sprite touches the catcher. → Inside a forever loop: if <touching [catcher]?> then change [Score] by 1.
2. Stop one touch from scoring hundreds of points. → After scoring, move the sprite away so it isn't touching anymore: go to x: (pick random -200 to 200) y: 150.
3. Take away a life when the sprite reaches the bottom of the screen. → if <y < -150> then change [Lives] by -1 then reset its position to the top.
4. End the game when lives reach 0. → if <Lives = 0> then broadcast [game over] → stop [all]; a sprite says "Game Over!" on when I receive [game over].
5. Show "You Win!" when the score reaches 10. → if <Score = 10> then broadcast [you win] → stop [all]; a sprite says "You Win!".
6. Make the game get harder as the player scores. → Store the fall speed in a Speed variable and change [Speed] by -1 every few points, so the sprite falls faster over time.

Going deeper (optional)

• True/false questions can be combined. Look at the green operator blocks: and, or, not. Build something like if <(touching [catcher]?) and (Score < 10)> then …. Invent a rule that needs two things to be true at once (for example, "touching the door and you have the key"). This deepens what a "condition" really is.
• Random makes replaying fun. Use pick random -200 to 200 for where the apple appears, and pick random 1 to 3 to choose which of three objects falls next. Why does a game feel more fun when it isn't exactly the same every time? This connects a small code trick to good game feel.

Common mistakes & fixes

If it's not working, check these common mix-ups:

• Mistake: the if/then is outside the forever loop, so the game only checks once at the start. → Fix: drag the if/then inside the forever loop so the question is asked continuously.
• Mistake: the score explodes because the sprites stay touching for many frames. → Fix: after scoring, move the sprite away (reset its position) so it stops touching.
• Mistake: the touching [ ]? dropdown points at the wrong sprite (or the edge), so collisions never register. → Fix: click the dropdown and pick the exact sprite to collide with.
• Mistake: stop all runs before the "You Win!" sprite can speak, so no message shows. → Fix: put the say block before stop all, or add a short wait so the message appears first.
• Mistake: using = when you mean "reached or passed," e.g. if Score = 10 but the score jumped from 9 to 11. → Fix: use > — if <Score > 9> catches it whether it lands on 10 or skips past.

What's next

Session 18 — Design & Showcase Your Game: you'll plan your own small game, build it using everything from this unit, playtest it with a partner, and present it to the class — the unit's build project.