Bubble Popper IV — Scratch L3 Lesson 20

Learnt28 min · escapes, lives, and ending the round
Basic24 min · the finished game
Challenge 1–327 min · harder, a lasting best, spiky bubbles
Extrabonus · ship it

WHAT IT SHOULD LOOK LIKE

Every bubble that reaches the surface costs a life. When the third one gets away the round stops by itself and the card comes up.

one gets away

out of lives

panels run left to right

Review — the arc so far 5 min

create clone of [myself v], a clone script, and delete this clone for every one of them.
Sprite-only variables give each clone its own speed, size and worth.
when this sprite clicked lands on the clone you hit.

Quick-fire

Your popping game runs for twenty-six bubbles and then stops, whether you are any good at it or not. What is missing?

Reveal the answer

A way to lose. A game needs a cost for failing and an ending that depends on how you played — and both of those come from the bubble that gets away.

Today’s Topic 3 min

A clone doing something on its way out, not just vanishing
lives, and why the decrement needs a guard
repeat until as the spawner’s loop, so the round ends itself
A difficulty that rises, and a best score that outlives the green flag

Learning outcome

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

Make a round end because of how the player played, not after a fixed count.
Build a difficulty curve with two blocks.
Keep a best score across several rounds.

Learnt — escaping, and losing 28 min

1 · The clone reports on its way out

Up to now a bubble reaching the surface just deleted itself. But that clone is the only thing in the project that knows it got away — so that is where the counting belongs:


when I start as a clone
show
repeat until <(y position) > (165)>
  change y by (speed)
end
change [escaped v] by (1)
delete this clone

One block between the loop and the delete. A bubble you popped never reaches it, because the click deleted the clone first.

WHAT IT SHOULD LOOK LIKE

A clone can do something on its way out. Up to now it only deleted itself; now it reports that it got away first.

two counters

Runs here in the page. Nothing to install.

How to use this: Click the green flag and pop some but not all. The two counters split between you and the bubbles.

Popped and escaped. Every bubble ends up in exactly one of the two.

2 · Lives

Turn the escape counter into a cost. lives is shared — there is one player — and starts at 3:


repeat until <(y position) > (165)>
  change y by (speed)
end
if <(lives) > (0)> then
  change [lives v] by (-1)
end
delete this clone

The if is not optional. Read on.

3 · A round that ends itself

The spawner has been using repeat (26), which means the round lasts the same length however you play. Swap the loop:


repeat (26)
  go to x: (pick random (-175) to (175)) y: (-170)
  create clone of [myself v]
  wait (0.3) seconds
end

Before — a fixed-length round.


repeat until <(lives) = (0)>
  go to x: (pick random (-175) to (175)) y: (-170)
  create clone of [myself v]
  wait (0.3) seconds
end

After — the round lasts as long as you do.

One word changed, and the game got a proper shape: it now depends on the player. Then wait a moment for the last clones to clear, and show the card.

WHAT IT SHOULD LOOK LIKE

The spawner stops watching the clock and starts watching the lives. It keeps making bubbles until there are none left.

three lives

none left, and it stops

panels run left to right

Runs here in the page. Nothing to install.

How to use this: Click the green flag and let three bubbles escape on purpose. The spawner stops on its own.

Nothing tells the spawner to stop. It simply runs out of the condition that kept it going.

Basic — the finished game 24 min

Open last lesson’s popping game. Four changes and it is a real game.

Step 1 — lives

Make lives, for all sprites, and show it.
Set it to 3 under the green flag, before anything else.

Step 2 — escaping costs

In the clone script, after the rise loop, add if <(lives) > (0)> then.
Inside it: change [lives v] by (-1).
Leave delete this clone below the whole thing.

Step 3 — the round ends itself

Swap the spawner’s repeat (26) for repeat until <(lives) = (0)>.
Run it. Play badly on purpose and watch it stop.

Step 4 — the game-over card

After the loop, wait about a second for the last bubbles to clear.
Bring the original to the middle, set it large, show it.
Say the totals, then say Game over., then hide.


when flag clicked
hide
set [lives v] to (3)
set [score v] to (0)
set [popped v] to (0)
repeat until <(lives) = (0)>
  go to x: (pick random (-175) to (175)) y: (-170)
  set [my size v] to (pick random (20) to (62))
  set [speed v] to (round ((10) - ((my size) / (10))))
  set [worth v] to (round ((8) - ((my size) / (10))))
  switch costume to (pick random (1) to (5))
  create clone of [myself v]
  wait (0.4) seconds
end
wait (1) seconds
go to x: (0) y: (0)
set size to (60) %
show
say (join [Popped ] (join (popped) (join [ for ] (score)))) for (2.5) seconds
say [Game over.] for (3) seconds
hide

The whole spawner, start to card. Twelve lines, and a real game.

Runs here in the page. Nothing to install.

How to use this: Click the green flag and play properly. Let three bubbles past and the game ends.

What you are aiming at. Lives, a score from each bubble's own worth, and a card at the end.

No bubbles appear at all.

lives is 0 when the loop is reached — the set [lives v] to (3) is missing or is below the loop.

Lives goes to −3 and the card is late.

The guard is missing. The bubbles still in flight when the round ended are taking lives they should not.

The game never ends however many escape.

The decrement is in the click script instead of after the rise loop, so only popping costs you lives — the opposite of the rule.

The card never appears.

A forever loop where a repeat until belongs, or a stop [all v] before the card.

The card appears while bubbles are still rising.

The wait after the loop is too short. A second or two covers the slowest bubble’s trip to the surface.

CHALLENGE 1 · L3-20-M1🪙 30 Adcoins8 min

It gets harder

A flat game is boring. Make the bubbles come faster the longer you survive.

A gap variable used by the wait, instead of a fixed number.
Every sixth bubble, the gap shrinks by a fifth.
The gap is visible, so you can watch the game tighten.

WHAT IT SHOULD LOOK LIKE

Challenge 1 — the gap between bubbles shrinks every six spawns, so a long run gets genuinely hard.

early on · a gap of 0.5

later · a gap of 0.2

panels run left to right

Runs here in the page. Nothing to install.

How to use this: Click the green flag and survive as long as you can. Watch the gap box shrink.

Five lives, and a gap that closes every six spawns. The last thirty seconds are frantic.

Done when: the gap is visibly smaller after twenty bubbles than after five, and the game is harder because of it.

Teacher reveal — every sixth one


change [made v] by (1)
if <((made) mod (6)) = (0)> then
  set [gap v] to ((gap) * (0.8))
end
wait (gap) seconds

mod from Lesson 3-2, doing real work: “is this a multiple of six?”. Multiplying by 0.8 rather than subtracting keeps the gap positive for ever, which subtracting would not.

CHALLENGE 2 · L3-20-M2🪙 50 Adcoins9 min

A best that lasts

Play three rounds without touching the green flag, and keep the highest score across all of them.

A key starts a round, not the flag.
score resets each round; best never does.
A new best is announced when it happens.

WHAT IT SHOULD LOOK LIKE

Challenge 2 — a best score that the green flag does not wipe. Three rounds in, it is still holding the highest.

round 3, a weaker run

Runs here in the page. Nothing to install.

How to use this: Click the green flag, then press G several times. Watch best hold while score changes.

Three rounds, three scores, one best. The flag sets it to 0 once and then leaves it alone.

Done when: a weak round after a strong one leaves best untouched.

Teacher reveal — where the reset goes


when flag clicked
set [best v] to (0)

when [g v] key pressed
set [score v] to (0)

Two hats, and the whole idea is which one holds which reset. Same shape as the Line Follower’s lap record and the Quiz Master’s best — say so, because a pupil who spots the repeat is generalising.

CHALLENGE 3 · L3-20-M3🪙 70 Adcoins10 min

Spiky bubbles

Some bubbles must not be popped. Roughly one in four is orange and spiky, and clicking it costs a life.

A sprite-only spiky, 1 or 0, decided before the clone is made.
A spiky bubble is a different colour, obviously.
Clicking a spiky one loses a life; clicking a normal one scores.
A count of how many mistakes you made.

WHAT IT SHOULD LOOK LIKE

Challenge 3 — the orange ones are spiky. Pop one and it costs a life, so every clone has to know which kind it is.

do not touch the orange one

Runs here in the page. Nothing to install.

How to use this: Click the green flag and pop only the blue ones. The orange ones bite.

Five lives. Every clone checks its own spiky before deciding what a click means.

Done when: clicking orange never scores, clicking blue never costs, and the mistake count at the end matches what you did.

Teacher reveal — the click branches on the clone’s own kind


when this sprite clicked
if <(spiky) = (1)> then
  change [lives v] by (-1)
  change [spiky popped v] by (1)
else
  change [score v] by (1)
end
delete this clone

If spiky is shared, every click is judged by the newest bubble’s kind and the game becomes random. It is the same bug as Lesson 3-19’s shared worth, and by now they should predict it before you run it.

EXTRA MISSION · L3-20-MX🪙 100 Adcoinsbonus

Ship it

Put the whole arc into one project you would be happy to hand to somebody else to play.

A title before the first bubble.
Three lives, and a round that ends itself.
Sizes, speeds and worths rolled per bubble.
A rising difficulty, golden bubbles, and a visible burst.
A score card, and a best that survives the round.

WHAT IT SHOULD LOOK LIKE

Extra — the finished game: a title, three lives, a rising difficulty, golden bubbles, a burst, and a best that lasts.

the title

in play

game over

panels run left to right

Runs here in the page. Nothing to install.

How to use this: Click the green flag, wait for the title, and play. Golden ones are worth twelve.

The finished arc in one project: clones, sprite-only variables, clicks, lives and a lasting best.

Teacher note

Worth counting the blocks with them. The shipped game is not much bigger than the Lesson 3-17 stream — almost everything added was a variable with the right scope, not more code. That is the message of the whole arc.

Summary 5 min

A clone can act on its way out — counting the escape belongs to the clone.
repeat until <(lives) = (0)> makes the round last as long as the player does.
Guard the decrement with if <(lives) > (0)> then, or bubbles still in flight take lives you have not got.
A gap variable multiplied by 0.8 is a difficulty curve in two blocks.
best resets under the flag; score resets each round.

Escape: A bubble reaching the surface unpopped.
Guard: An if that stops a change happening when it should not.
Difficulty curve: A game getting harder the longer it lasts.
Game over card: The original sprite reappearing to report the run.

Hand in

Save your shipped game. You have finished the clones arc — one sprite, three hundred bubbles, and every one of them knowing its own business.

Learnt28 min · escapes, lives, and ending the round
Basic24 min · the finished game
Challenge 1–327 min · harder, a lasting best, spiky bubbles
Extrabonus · ship it

WHAT IT SHOULD LOOK LIKE

Every bubble that reaches the surface costs a life. When the third one gets away the round stops by itself and the card comes up.

one gets away

out of lives

panels run left to right

Review — the arc so far 5 min

create clone of [myself v], a clone script, and delete this clone for every one of them.
Sprite-only variables give each clone its own speed, size and worth.
when this sprite clicked lands on the clone you hit.

Quick-fire

Your popping game runs for twenty-six bubbles and then stops, whether you are any good at it or not. What is missing?

Reveal the answer

A way to lose. A game needs a cost for failing and an ending that depends on how you played — and both of those come from the bubble that gets away.

Today’s Topic 3 min

A clone doing something on its way out, not just vanishing
lives, and why the decrement needs a guard
repeat until as the spawner’s loop, so the round ends itself
A difficulty that rises, and a best score that outlives the green flag

Learning outcome

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

Make a round end because of how the player played, not after a fixed count.
Build a difficulty curve with two blocks.
Keep a best score across several rounds.

Learnt — escaping, and losing 28 min

1 · The clone reports on its way out

Up to now a bubble reaching the surface just deleted itself. But that clone is the only thing in the project that knows it got away — so that is where the counting belongs:


when I start as a clone
show
repeat until <(y position) > (165)>
  change y by (speed)
end
change [escaped v] by (1)
delete this clone

One block between the loop and the delete. A bubble you popped never reaches it, because the click deleted the clone first.

WHAT IT SHOULD LOOK LIKE

A clone can do something on its way out. Up to now it only deleted itself; now it reports that it got away first.

two counters

Runs here in the page. Nothing to install.

How to use this: Click the green flag and pop some but not all. The two counters split between you and the bubbles.

Popped and escaped. Every bubble ends up in exactly one of the two.

2 · Lives

Turn the escape counter into a cost. lives is shared — there is one player — and starts at 3:


repeat until <(y position) > (165)>
  change y by (speed)
end
if <(lives) > (0)> then
  change [lives v] by (-1)
end
delete this clone

The if is not optional. Read on.

3 · A round that ends itself

The spawner has been using repeat (26), which means the round lasts the same length however you play. Swap the loop:


repeat (26)
  go to x: (pick random (-175) to (175)) y: (-170)
  create clone of [myself v]
  wait (0.3) seconds
end

Before — a fixed-length round.


repeat until <(lives) = (0)>
  go to x: (pick random (-175) to (175)) y: (-170)
  create clone of [myself v]
  wait (0.3) seconds
end

After — the round lasts as long as you do.

One word changed, and the game got a proper shape: it now depends on the player. Then wait a moment for the last clones to clear, and show the card.

WHAT IT SHOULD LOOK LIKE

The spawner stops watching the clock and starts watching the lives. It keeps making bubbles until there are none left.

three lives

none left, and it stops

panels run left to right

Runs here in the page. Nothing to install.

How to use this: Click the green flag and let three bubbles escape on purpose. The spawner stops on its own.

Nothing tells the spawner to stop. It simply runs out of the condition that kept it going.

Basic — the finished game 24 min

Open last lesson’s popping game. Four changes and it is a real game.

Step 1 — lives

Make lives, for all sprites, and show it.
Set it to 3 under the green flag, before anything else.

Step 2 — escaping costs

In the clone script, after the rise loop, add if <(lives) > (0)> then.
Inside it: change [lives v] by (-1).
Leave delete this clone below the whole thing.

Step 3 — the round ends itself

Swap the spawner’s repeat (26) for repeat until <(lives) = (0)>.
Run it. Play badly on purpose and watch it stop.

Step 4 — the game-over card

After the loop, wait about a second for the last bubbles to clear.
Bring the original to the middle, set it large, show it.
Say the totals, then say Game over., then hide.


when flag clicked
hide
set [lives v] to (3)
set [score v] to (0)
set [popped v] to (0)
repeat until <(lives) = (0)>
  go to x: (pick random (-175) to (175)) y: (-170)
  set [my size v] to (pick random (20) to (62))
  set [speed v] to (round ((10) - ((my size) / (10))))
  set [worth v] to (round ((8) - ((my size) / (10))))
  switch costume to (pick random (1) to (5))
  create clone of [myself v]
  wait (0.4) seconds
end
wait (1) seconds
go to x: (0) y: (0)
set size to (60) %
show
say (join [Popped ] (join (popped) (join [ for ] (score)))) for (2.5) seconds
say [Game over.] for (3) seconds
hide

The whole spawner, start to card. Twelve lines, and a real game.

Runs here in the page. Nothing to install.

How to use this: Click the green flag and play properly. Let three bubbles past and the game ends.

What you are aiming at. Lives, a score from each bubble's own worth, and a card at the end.

No bubbles appear at all.

lives is 0 when the loop is reached — the set [lives v] to (3) is missing or is below the loop.

Lives goes to −3 and the card is late.

The guard is missing. The bubbles still in flight when the round ended are taking lives they should not.

The game never ends however many escape.

The decrement is in the click script instead of after the rise loop, so only popping costs you lives — the opposite of the rule.

The card never appears.

A forever loop where a repeat until belongs, or a stop [all v] before the card.

The card appears while bubbles are still rising.

The wait after the loop is too short. A second or two covers the slowest bubble’s trip to the surface.

CHALLENGE 1 · L3-20-M1🪙 30 Adcoins8 min

It gets harder

A flat game is boring. Make the bubbles come faster the longer you survive.

A gap variable used by the wait, instead of a fixed number.
Every sixth bubble, the gap shrinks by a fifth.
The gap is visible, so you can watch the game tighten.

WHAT IT SHOULD LOOK LIKE

Challenge 1 — the gap between bubbles shrinks every six spawns, so a long run gets genuinely hard.

early on · a gap of 0.5

later · a gap of 0.2

panels run left to right

Runs here in the page. Nothing to install.

How to use this: Click the green flag and survive as long as you can. Watch the gap box shrink.

Five lives, and a gap that closes every six spawns. The last thirty seconds are frantic.

Done when: the gap is visibly smaller after twenty bubbles than after five, and the game is harder because of it.

Teacher reveal — every sixth one


change [made v] by (1)
if <((made) mod (6)) = (0)> then
  set [gap v] to ((gap) * (0.8))
end
wait (gap) seconds

mod from Lesson 3-2, doing real work: “is this a multiple of six?”. Multiplying by 0.8 rather than subtracting keeps the gap positive for ever, which subtracting would not.

CHALLENGE 2 · L3-20-M2🪙 50 Adcoins9 min

A best that lasts

Play three rounds without touching the green flag, and keep the highest score across all of them.

A key starts a round, not the flag.
score resets each round; best never does.
A new best is announced when it happens.

WHAT IT SHOULD LOOK LIKE

Challenge 2 — a best score that the green flag does not wipe. Three rounds in, it is still holding the highest.

round 3, a weaker run

Runs here in the page. Nothing to install.

How to use this: Click the green flag, then press G several times. Watch best hold while score changes.

Three rounds, three scores, one best. The flag sets it to 0 once and then leaves it alone.

Done when: a weak round after a strong one leaves best untouched.

Teacher reveal — where the reset goes


when flag clicked
set [best v] to (0)

when [g v] key pressed
set [score v] to (0)

CHALLENGE 3 · L3-20-M3🪙 70 Adcoins10 min

Spiky bubbles

Some bubbles must not be popped. Roughly one in four is orange and spiky, and clicking it costs a life.

A sprite-only spiky, 1 or 0, decided before the clone is made.
A spiky bubble is a different colour, obviously.
Clicking a spiky one loses a life; clicking a normal one scores.
A count of how many mistakes you made.

WHAT IT SHOULD LOOK LIKE

Challenge 3 — the orange ones are spiky. Pop one and it costs a life, so every clone has to know which kind it is.

do not touch the orange one

Runs here in the page. Nothing to install.

How to use this: Click the green flag and pop only the blue ones. The orange ones bite.

Five lives. Every clone checks its own spiky before deciding what a click means.

Done when: clicking orange never scores, clicking blue never costs, and the mistake count at the end matches what you did.

Teacher reveal — the click branches on the clone’s own kind


when this sprite clicked
if <(spiky) = (1)> then
  change [lives v] by (-1)
  change [spiky popped v] by (1)
else
  change [score v] by (1)
end
delete this clone

EXTRA MISSION · L3-20-MX🪙 100 Adcoinsbonus

Ship it

Put the whole arc into one project you would be happy to hand to somebody else to play.

A title before the first bubble.
Three lives, and a round that ends itself.
Sizes, speeds and worths rolled per bubble.
A rising difficulty, golden bubbles, and a visible burst.
A score card, and a best that survives the round.

WHAT IT SHOULD LOOK LIKE

Extra — the finished game: a title, three lives, a rising difficulty, golden bubbles, a burst, and a best that lasts.

the title

in play

game over

panels run left to right

Runs here in the page. Nothing to install.

How to use this: Click the green flag, wait for the title, and play. Golden ones are worth twelve.

The finished arc in one project: clones, sprite-only variables, clicks, lives and a lasting best.

Teacher note

Summary 5 min

A clone can act on its way out — counting the escape belongs to the clone.
repeat until <(lives) = (0)> makes the round last as long as the player does.
Guard the decrement with if <(lives) > (0)> then, or bubbles still in flight take lives you have not got.
A gap variable multiplied by 0.8 is a difficulty curve in two blocks.
best resets under the flag; score resets each round.

Escape: A bubble reaching the surface unpopped.
Guard: An if that stops a change happening when it should not.
Difficulty curve: A game getting harder the longer it lasts.
Game over card: The original sprite reappearing to report the run.

Hand in

Save your shipped game. You have finished the clones arc — one sprite, three hundred bubbles, and every one of them knowing its own business.