Score & Lives Counter — your first full mini-game

Learning Goals 3 min

By the end of this lesson you will be able to:

1. Combine two variables — score and lives — that work together in a single game loop, each tracking a different thing.
2. Wire when this sprite clicked to change [score v] by (1) for hits, and a missed-window pattern to change [lives v] by (-1) for misses.
3. End the game with if <(lives) = (0)> then → stop [all v] — a game-over check that runs every frame inside the forever loop.

Warm-Up — what would a complete tiny game look like? 7 min

For the last three lessons, you've practiced variables one piece at a time — making them, naming them, picking scope, resetting them. Today we glue all of it together into something a friend could actually play.

The game is Tap-the-Cat. Rules:

• The cat appears at a random spot on the Stage every 2 seconds.
• If you click the cat before it moves, you score 1 point.
• If the cat moves away before you click it, you lose 1 life.
• You start with 3 lives. When lives hit 0, the game stops.

That's it. Tiny game. But notice what it needs:

1. Two variables — score goes up, lives goes down.
2. A reset at the start so each new flag click is a clean game.
3. A random-position loop with a 2-second wait.
4. A click handler that runs in parallel with the random-position loop.
5. A game-over check that runs every frame.
6. Watcher widgets on the Stage so the player can see score and lives.

New Concept — variables working in pairs 15 min

Until now, every project you've built has touched one variable at a time. Real games have several variables that react to each other — score goes up when you do well, lives go down when you do badly, level goes up when score reaches a threshold. Today you'll wire two of them together.

Two variables, two directions

In Tap-the-Cat, score and lives point in opposite directions:

• score starts at 0, goes up when good things happen. change [score v] by (1).
• lives starts at 3, goes down when bad things happen. change [lives v] by (-1).

Both are global (every sprite shares them — but in this game, the cat is the only sprite, so it doesn't matter much). Both get reset at the top of the flag-click stack.

Watcher widgets — telling the player

A variable nobody can see is no fun. Open the Variables palette and tick the checkbox next to score and lives. Two little boxes appear on the Stage showing the live value. Drag them where you want. Right-click a watcher for display options — normal readout, large readout, or slider. For games, use normal readout.

Parallel scripts — two hats, one sprite

A sprite can have multiple hat blocks, and Scratch runs them all at the same time. The cat sprite in this game has:

• A when ⚑ clicked hat that resets variables, then loops forever — move to random spot, wait 2 seconds, lose a life. This is the move-loop.
• A when this sprite clicked hat that fires whenever the user actually clicks the cat — add 1 to score. This is the click-handler.

These two scripts run in parallel. The move-loop is busy waiting and moving, regardless of what the player does. The click-handler sits silent until the player clicks — then it fires once and goes back to sleep. They share the same two variables.

The game-over check

Inside the move-loop's forever, after every life-losing event, check if lives have run out:

if <(lives) = (0)> then
  stop [all v]
end
        

Notice the equality operator () = () with lives on the left and 0 on the right. The check has to run after the change [lives v] by (-1), otherwise lives could go negative before anyone notices.

Worked Example — Tap-the-Cat from empty project to playable 12 min

Open Scratch. Eight steps to a complete game.

Step 1 — Start fresh

New project. Keep the default cat. That's our only sprite. Resize it down to about 70% so it's a slightly trickier target — drag the resize handle in the corner of the costume, or use the size box in the sprite info panel.

Step 2 — Make the two variables

Variables palette → Make a Variable. Name score, leave For all sprites ticked, OK. Repeat for lives. Tick the checkbox next to each so the watchers show on the Stage. Drag score to the top-left corner of the Stage, lives to the top-right.

Step 3 — Build the reset + move-loop

On the cat, build this stack:

when flag clicked
set [score v] to (0)
set [lives v] to (3)
forever
  go to x: (pick random (-200) to (200)) y: (pick random (-150) to (150))
  wait (2) seconds
  change [lives v] by (-1)
  if <(lives) = (0)> then
    stop [all v]
  end
end
        

Step 4 — Test the move-loop alone

Click the flag. The cat teleports around the Stage every 2 seconds. lives drops: 3, 2, 1, 0. At 0, everything stops. Game over fires correctly — but there's no way to score yet, because we haven't built the click-handler.

Step 5 — Build the click-handler

On the same cat, build a second stack (separate from the first):

when this sprite clicked
change [score v] by (1)
        

Step 6 — Click the flag and play

Cat teleports. Click it before it moves — score goes up by 1. Don't click it — wait 2 seconds and lives drops by 1. Lose all 3 lives and the game stops. You just made a game.

Step 7 — Add a "game over" message

Before the stop [all v] in the move-loop, sneak in a say [Game over!] for (2) seconds so the player knows why everything stopped. Tiny change, huge polish.

Step 8 — Adjust difficulty

Too easy? Drop the wait from 2 to 1 second. Cat moves twice as fast. Too hard? Boost the starting lives from 3 to 5. Make a friend playtest and adjust until they get a score of around 10 before game-over — that's good game-design balance.

The full assembled stacks

when flag clicked
set [score v] to (0)
set [lives v] to (3)
forever
  go to x: (pick random (-200) to (200)) y: (pick random (-150) to (150))
  wait (2) seconds
  change [lives v] by (-1)
  if <(lives) = (0)> then
    say [Game over!] for (2) seconds
    stop [all v]
  end
end
        

when this sprite clicked
change [score v] by (1)
        

What you just built: a complete arcade-style game. It has a start (reset), middle (loop with score and lives), and end (game over). It uses two variables that cooperate — one going up, one going down, both being watched, both reacting to player input. This is the template for every clicker, catcher, and dodger you'll build in Levels 3 and 4.

Try It Yourself — three remix drills 15 min

when this sprite clicked
change [score v] by (2)
          

when flag clicked
set [score v] to (0)
set [lives v] to (3)
forever
  go to x: (pick random (-200) to (200)) y: (pick random (-150) to (150))
  wait (2) seconds
  change [lives v] by (-1)
  if <(score) > (high score)> then
    set [high score v] to (score)
  end
  if <(lives) = (0)> then
    stop [all v]
  end
end
          

when flag clicked
forever
  go to x: (pick random (-200) to (200)) y: (pick random (-150) to (150))
  wait (2) seconds
  change [lives v] by (-1)
  if <(lives) = (0)> then
    stop [all v]
  end
end
          

Mini-Challenge — the cat that won't die 5 min

"Priya's invincible cat"

Priya built Tap-the-Cat and the score works fine — but the cat never runs out of lives. She watches lives on the Stage. It drops to 2, then 1, then 0… then -1, then -2, then -3, and the game keeps going forever. Here's her move-loop:

when flag clicked
set [score v] to (0)
set [lives v] to (3)
forever
  go to x: (pick random (-200) to (200)) y: (pick random (-150) to (150))
  wait (2) seconds
  if <(lives) = (0)> then
    stop [all v]
  end
  change [lives v] by (-1)
end
        

Why does lives sail past 0 into negative numbers without the game ever stopping?

when flag clicked
set [score v] to (0)
set [lives v] to (3)
forever
  go to x: (pick random (-200) to (200)) y: (pick random (-150) to (150))
  wait (2) seconds
  change [lives v] by (-1)
  if <(lives) = (0)> then
    stop [all v]
  end
end
          

Recap 3 min

You built a complete tiny game. The recipe was: two variables (one going up, one going down), a reset stack at the top of the flag-click script, a forever loop with random movement and a timed wait, a separate click-handler that fires in parallel, a game-over check immediately after the decrement, and watcher widgets on the Stage so the player can see what's happening. This is the entire skeleton of the Score & Lives HUD arc — every block you've learned in lessons 31 through 35 working together. Every clicker, catcher, dodger, racer, and shooter you build from here on will be a fancier version of this exact pattern.

Game loop

The main forever inside a game that handles movement, scoring, and the game-over check. Every frame: do, react, check.

Click-handler

A second hat-block stack (usually when this sprite clicked) that runs in parallel with the main game loop. Lets the player interact while the game keeps running.

Watcher widget

The little box on the Stage that shows a variable's live value. Tick the checkbox next to a variable name in the Variables palette to show it.

Game-over check

An if-then inside the game loop that watches for a losing condition (often (lives) = (0)) and runs stop [all v] when it fires.

stop all

stop [all v] — halts every script on every sprite in the project. The polite way to end a game.

Parallel scripts

Two or more hat blocks on the same sprite that all run at the same time. Each script does its own thing; they cooperate by sharing variables.

Homework 2 min

The Reskin. Take the finished Tap-the-Cat game and turn it into something else. Same skeleton, different theme.

1. Open your finished Tap-the-Cat project. Save a copy as HW-L2-36-MyGame.sb3.
2. Replace the cat sprite with anything else from the library (a star, a balloon, a piece of kuih, a teh-tarik glass — your choice).
3. Change the backdrop to match your theme. Aisyah might use a night sky for catch-the-star. Daniel might use a kitchen for catch-the-kuih.
4. Tune the difficulty: pick a wait time between 1 and 3 seconds, and a starting lives between 3 and 7. Playtest until you can score around 10 before losing.
5. Add one polish touch from this list: a sound when scoring (play sound [pop v] until done in the click-handler), a costume change on game-over, or a different colour effect at low lives.
6. Make sure your two variables, your reset stack, your game-over check, and your watchers are all in place. This is a cluster-F audit.

Save and bring it to class.

Bring back next class:

• Your reskinned HW-L2-36-MyGame.sb3 file.
• The high score you reached on your own game.
• Your answer to: "What variable would you add to make this game more interesting? (Examples: a combo counter, a level that speeds things up, a multiplier.) You don't have to build it — just describe."

Heads up for next class: SCR-L02-37 opens cluster G with a new game pattern — falling objects. You'll meet pick random () to () again, this time for a sprite's x coordinate, and you'll build apples that fall from the top of the Stage at random positions.