Storm Flight II — Scratch L3 Lesson 22

Learnt28 min · a crash, and three lives
Basic24 min · the game-over screen
Challenge 1–327 min · 60 touches, the hurt flag, the stale round
Extrabonus · rounds done right

WHAT IT SHOULD LOOK LIKE

Three lives, a crash that costs one, and a game-over screen you can start the next round from. The green flag stays untouched.

flying, three lives

hit — one life gone

out of lives

panels run left to right

Review — last lesson 5 min

A state variable holds a word naming the situation: title, play, over.
Every script asks the state before it acts. The one that forgets is the bug.
broadcast announces a change; the player’s own key replaces the green flag.

Quick-fire

Your game reaches the over state after a fixed number of ticks, however well or badly the player flew. What is missing?

Reveal the answer

A reason to lose. The round has to end because of something the player did — and that means a cost for being hit.

Today’s Topic 3 min

touching (Bolt v)? ending the round
lives, and why one bolt can take all three in a fifth of a second
A hurt flag, and a cool-down script of its own
Where a reset belongs — under the flag, or at the start of a round

Learning outcome

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

End a round because of how the player played.
Stop a single collision being counted sixty times.
Say which of your resets belongs in which script, and why.

Learnt — crashing, and lives 28 min

1 · One touch ends it

The simplest way to lose: touching a bolt sets the state to over. Because every script asks the state, nothing needs telling twice — the bolt hides itself, the flying loop falls out, and the whole Stage stops together.


repeat until <not <(state) = [play]>>
  next costume
  if <touching (Bolt v)?> then
    set [state v] to [over]
  end
end

Two blocks to lose a game. The loop’s own condition then does the stopping.

WHAT IT SHOULD LOOK LIKE

One touch sets the state to over, and because every script asks the state, the whole Stage stops at the same moment.

the moment of contact

everything stops together

panels run left to right

Runs here in the page. Nothing to install.

How to use this: Click the green flag and fly into the bolt with the arrow keys.

One touch. The state goes to over and everything that was asking it stops at once.

2 · Three lives instead of one

One hit is harsh. Make lives — shared, because there is one player — and spend one per hit:


if <touching (Bolt v)?> then
  change [lives v] by (-1)
  set [ghost v] effect to (50)
  go to x: (-150) y: (0)
  wait (0.35) seconds
  clear graphic effects
  if <(lives) = (0)> then
    set [state v] to [over]
  end
end

The four blocks between the change and the check are not decoration. They are the whole of Challenges 1 and 2.

WHAT IT SHOULD LOOK LIKE

A hit costs one life and the round carries on. Only the last one ends it — which is why the parrot gets a moment of safety after each hit.

hit, and moved to safety

Runs here in the page. Nothing to install.

How to use this: Click the green flag and fly. The bolt hunts you, so all three lives will go.

Lives 3 to 0, and the round ends on the last one — not the first.

The bolt hunts. It uses point towards (Parrot v) then move (9) steps, and then points back to 90 so it stays upright. A hazard that goes where the player is makes a far better demonstration than one that flies a fixed path and misses.

3 · Why a hit needs a moment of safety

Scratch checks that if about thirty times a second. A parrot overlapping a bolt is still overlapping it on the next frame, and the next. So one collision is not one hit — it is one hit per frame for as long as you are touching.

That is why the parrot is moved away and made see-through for a moment. Challenge 1 takes those blocks out so you can measure exactly how bad it is; Challenge 2 puts back something better.

Basic — the game-over screen 24 min

Open last lesson’s Storm Flight. You are giving it a way to end, and a way to begin again.

Step 1 — lives

Make lives, for all sprites, and show it.
Make rounds too — it is how you will prove the play-again works.

Step 2 — reset where the round starts

In the when I receive [start v] script, set state to play and lives to 3.
Add change [rounds v] by (1).
Leave the green flag doing nothing but going to the title. This matters. See Challenge 3.

Step 3 — the hazard

Add the Lightning sprite and call it Bolt.
Give it the shape from last lesson: a forever loop that asks the state, shows itself in play and hides otherwise.
Inside play: point towards (Parrot v), move (9) steps, point in direction (90).

Step 4 — losing a life

In the flying loop, test for touching the bolt.
Lose a life, go see-through, fly home, wait a third of a second, clear the effect.
If lives reached 0, set the state to over.

Step 5 — the screen

After the loop, bring the parrot to the middle and make it bigger.
Say GAME OVER, then Press space to play again.
Make sure your space-key script sends start when the state is over.

Runs here in the page. Nothing to install.

How to use this: Click the green flag, press space to play, lose all three lives, then press space again.

What you are aiming at. Lives 3 to 0, a screen, and a second round without the flag.

All three lives go the instant I touch a bolt.

The wait and the move-away are missing. This is Challenge 1, and it is worth building deliberately before you fix it.

The round never ends, however many times I am hit.

The if <(lives) = (0)> then is outside the touching check, or lives skipped past 0 into negatives so it never equalled 0 exactly. Use <(lives) < (1)> if you are unsure.

The bolt keeps chasing after the game is over.

Its loop is not asking the state. Same bug as last lesson’s Challenge 1.

The bolt turns upside down as it chases.

point towards rotates the sprite. Add point in direction (90) straight after the move, or set the rotation style to “do not rotate”.

The second round starts with no lives.

Your reset is under the green flag. That is Challenge 3 — and it is the single most common bug in this whole arc.

CHALLENGE 1 · L3-22-M1🪙 30 Adcoins8 min

One bolt, sixty hits

Measure the bug rather than being told about it.

Park the parrot inside a stationary bolt and leave it there.
Run the loop exactly 60 times — repeat (60) with a tiny wait, so it is about two seconds.
Count touches as well as lives, and take the guard out completely.

WHAT IT SHOULD LOOK LIKE

Challenge 1 — one bolt, sixty frames, and the parrot sitting in it. The test is true on every single frame, so lives falls off a cliff.

60 frames later

Runs here in the page. Nothing to install.

How to use this: Click the green flag and just watch. The parrot does not move and neither does the bolt.

Sixty frames, sixty touches, and lives at −57. One collision, counted every frame.

Done when: your touches counter equals your repeat count, and you can explain why those two numbers are the same.

Teacher note

Ask for a prediction before running it. Most pupils guess 1, or 3. The answer being exactly the loop count is the thing that makes “per frame, not per event” land.

CHALLENGE 2 · L3-22-M2🪙 50 Adcoins9 min

The hurt flag

Fix it properly. Everything stays exactly as it was in Challenge 1 — same sixty frames, same stationary bolt, same parrot sitting in it — and you add one variable.

A hurt variable, 0 or 1.
The hit only counts when hurt is 0.
A separate script clears it after 0.4 seconds.

WHAT IT SHOULD LOOK LIKE

Challenge 2 — the same bolt, the same sixty frames, the same parrot sitting in it. The only difference is a hurt flag, and the damage drops sevenfold.

hurt = 0 · the hit counts

hurt = 1 · the next 0.4s cost nothing

60 frames later

panels run left to right

The ghost effect does not make you safe. A see-through sprite is still touching. touching (Bolt v)? does not care what you look like. The safety has to be a decision your code makes, and that decision is the hurt flag.

Runs here in the page. Nothing to install.

How to use this: Click the green flag and watch the hurt box flick between 1 and 0 as the touches creep up.

Sixty frames again. Nine touches instead of sixty — and the only change is one variable.

Done when: you can put the two numbers side by side — 60 and 9 — and point at the one line of code that is different.

Why does the fixed version still end on minus lives?

Because the cool-down fixes the rate of damage, not the floor. Nine hits on three lives is still −6. Stopping at zero is a separate guard — the if <(lives) > (0)> then you met in Lesson 3-20 — and a finished game needs both. Ask pupils to add it and watch the number land on 0.

Teacher reveal — why the cool-down must be its own script


when I receive [cool down v]
set [ghost v] effect to (55)
wait (0.4) seconds
clear graphic effects
set [hurt v] to (0)

Put that wait inside the main loop instead and the loop stops for 0.4 seconds — the parrot freezes mid-game and the fix is worse than the bug. A broadcast starts a second script that waits alongside the first. That is the real lesson here, and it is the same reasoning as the pause script next lesson.

CHALLENGE 3 · L3-22-M3🪙 70 Adcoins10 min

The stale round

Move your resets under the green flag, play two rounds, and watch the second one start already broken.

set [lives v] to (3) under the flag, not in the round.
Two rounds back to back, with two hits each.
Write down what round two started with.

WHAT IT SHOULD LOOK LIKE

Challenge 3 — the reset put under the green flag instead of at the start of a round. Round two begins on whatever round one left behind.

round 1 ends on 1 life

round 2 begins on 1 life

panels run left to right

Runs here in the page. Nothing to install.

How to use this: Click the green flag and read the speech bubbles. Two rounds run one after the other.

Round 1 ends on 1 life. Round 2 therefore BEGINS on 1 life and ends on −1.

Done when: you can state the rule in your own words, and point at each of your own resets and say which script it belongs in.

Teacher reveal — the rule

A reset belongs in the script that owns the thing being reset.

Under the flag: things that should outlast a round — the high score, the number of rounds played, the difficulty setting.
At the start of a round: things the round owns — lives, score, position, effects, leftover clones.

Ask them to list every variable in their project under one of those two headings. It takes four minutes and prevents most of the bugs in the next three arcs.

EXTRA MISSION · L3-22-MX🪙 100 Adcoinsbonus

Rounds done right

Three rounds in a row, each one starting clean, and a best score that survives all three.

The flag sets up only what outlasts a round.
The round resets only what it owns.
A best that never goes down.

Runs here in the page. Nothing to install.

How to use this: Click the green flag and let three rounds play out. Watch best against stars.

Three rounds, each clean, and a best of 23 that no later round could wipe.

Teacher note

This is the pattern the rest of Level 3 assumes. If a pupil’s next game has a score that resets oddly, come back to this project rather than debugging the new one — the shape is easier to see here.

Summary 5 min

touching (Bolt v)? plus set [state v] to [over] is a game you can lose.
A collision is tested every frame, so one touch is many hits unless you stop it.
The ghost effect does not make you safe. A hurt flag does — 60 touches became 9.
The cool-down goes in a script of its own, or the wait freezes the game.
A reset belongs in the script that owns the thing: the flag for what outlasts a round, the round for what it owns.

Lives: How many hits are left before the round ends.
Cool-down: A short time after an event during which it cannot happen again.
Flag variable: A variable holding 0 or 1, used as a yes-or-no answer.
Stale state: A new round starting on the last round’s leftovers.

Hand in

Save your game. Next lesson is the one that tests whether your state machine really works: pause.

Learnt28 min · a crash, and three lives
Basic24 min · the game-over screen
Challenge 1–327 min · 60 touches, the hurt flag, the stale round
Extrabonus · rounds done right

WHAT IT SHOULD LOOK LIKE

Three lives, a crash that costs one, and a game-over screen you can start the next round from. The green flag stays untouched.

flying, three lives

hit — one life gone

out of lives

panels run left to right

Review — last lesson 5 min

A state variable holds a word naming the situation: title, play, over.
Every script asks the state before it acts. The one that forgets is the bug.
broadcast announces a change; the player’s own key replaces the green flag.

Quick-fire

Your game reaches the over state after a fixed number of ticks, however well or badly the player flew. What is missing?

Reveal the answer

A reason to lose. The round has to end because of something the player did — and that means a cost for being hit.

Today’s Topic 3 min

touching (Bolt v)? ending the round
lives, and why one bolt can take all three in a fifth of a second
A hurt flag, and a cool-down script of its own
Where a reset belongs — under the flag, or at the start of a round

Learning outcome

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

End a round because of how the player played.
Stop a single collision being counted sixty times.
Say which of your resets belongs in which script, and why.

Learnt — crashing, and lives 28 min

1 · One touch ends it


repeat until <not <(state) = [play]>>
  next costume
  if <touching (Bolt v)?> then
    set [state v] to [over]
  end
end

Two blocks to lose a game. The loop’s own condition then does the stopping.

WHAT IT SHOULD LOOK LIKE

One touch sets the state to over, and because every script asks the state, the whole Stage stops at the same moment.

the moment of contact

everything stops together

panels run left to right

Runs here in the page. Nothing to install.

How to use this: Click the green flag and fly into the bolt with the arrow keys.

One touch. The state goes to over and everything that was asking it stops at once.

2 · Three lives instead of one

One hit is harsh. Make lives — shared, because there is one player — and spend one per hit:


if <touching (Bolt v)?> then
  change [lives v] by (-1)
  set [ghost v] effect to (50)
  go to x: (-150) y: (0)
  wait (0.35) seconds
  clear graphic effects
  if <(lives) = (0)> then
    set [state v] to [over]
  end
end

The four blocks between the change and the check are not decoration. They are the whole of Challenges 1 and 2.

WHAT IT SHOULD LOOK LIKE

A hit costs one life and the round carries on. Only the last one ends it — which is why the parrot gets a moment of safety after each hit.

hit, and moved to safety

Runs here in the page. Nothing to install.

How to use this: Click the green flag and fly. The bolt hunts you, so all three lives will go.

Lives 3 to 0, and the round ends on the last one — not the first.

3 · Why a hit needs a moment of safety

That is why the parrot is moved away and made see-through for a moment. Challenge 1 takes those blocks out so you can measure exactly how bad it is; Challenge 2 puts back something better.

Basic — the game-over screen 24 min

Open last lesson’s Storm Flight. You are giving it a way to end, and a way to begin again.

Step 1 — lives

Make lives, for all sprites, and show it.
Make rounds too — it is how you will prove the play-again works.

Step 2 — reset where the round starts

In the when I receive [start v] script, set state to play and lives to 3.
Add change [rounds v] by (1).
Leave the green flag doing nothing but going to the title. This matters. See Challenge 3.

Step 3 — the hazard

Add the Lightning sprite and call it Bolt.
Give it the shape from last lesson: a forever loop that asks the state, shows itself in play and hides otherwise.
Inside play: point towards (Parrot v), move (9) steps, point in direction (90).

Step 4 — losing a life

In the flying loop, test for touching the bolt.
Lose a life, go see-through, fly home, wait a third of a second, clear the effect.
If lives reached 0, set the state to over.

Step 5 — the screen

After the loop, bring the parrot to the middle and make it bigger.
Say GAME OVER, then Press space to play again.
Make sure your space-key script sends start when the state is over.

Runs here in the page. Nothing to install.

How to use this: Click the green flag, press space to play, lose all three lives, then press space again.

What you are aiming at. Lives 3 to 0, a screen, and a second round without the flag.

All three lives go the instant I touch a bolt.

The wait and the move-away are missing. This is Challenge 1, and it is worth building deliberately before you fix it.

The round never ends, however many times I am hit.

The if <(lives) = (0)> then is outside the touching check, or lives skipped past 0 into negatives so it never equalled 0 exactly. Use <(lives) < (1)> if you are unsure.

The bolt keeps chasing after the game is over.

Its loop is not asking the state. Same bug as last lesson’s Challenge 1.

The bolt turns upside down as it chases.

point towards rotates the sprite. Add point in direction (90) straight after the move, or set the rotation style to “do not rotate”.

The second round starts with no lives.

Your reset is under the green flag. That is Challenge 3 — and it is the single most common bug in this whole arc.

CHALLENGE 1 · L3-22-M1🪙 30 Adcoins8 min

One bolt, sixty hits

Measure the bug rather than being told about it.

Park the parrot inside a stationary bolt and leave it there.
Run the loop exactly 60 times — repeat (60) with a tiny wait, so it is about two seconds.
Count touches as well as lives, and take the guard out completely.

WHAT IT SHOULD LOOK LIKE

Challenge 1 — one bolt, sixty frames, and the parrot sitting in it. The test is true on every single frame, so lives falls off a cliff.

60 frames later

Runs here in the page. Nothing to install.

How to use this: Click the green flag and just watch. The parrot does not move and neither does the bolt.

Sixty frames, sixty touches, and lives at −57. One collision, counted every frame.

Done when: your touches counter equals your repeat count, and you can explain why those two numbers are the same.

Teacher note

Ask for a prediction before running it. Most pupils guess 1, or 3. The answer being exactly the loop count is the thing that makes “per frame, not per event” land.

CHALLENGE 2 · L3-22-M2🪙 50 Adcoins9 min

The hurt flag

Fix it properly. Everything stays exactly as it was in Challenge 1 — same sixty frames, same stationary bolt, same parrot sitting in it — and you add one variable.

A hurt variable, 0 or 1.
The hit only counts when hurt is 0.
A separate script clears it after 0.4 seconds.

WHAT IT SHOULD LOOK LIKE

Challenge 2 — the same bolt, the same sixty frames, the same parrot sitting in it. The only difference is a hurt flag, and the damage drops sevenfold.

hurt = 0 · the hit counts

hurt = 1 · the next 0.4s cost nothing

60 frames later

panels run left to right

Runs here in the page. Nothing to install.

How to use this: Click the green flag and watch the hurt box flick between 1 and 0 as the touches creep up.

Sixty frames again. Nine touches instead of sixty — and the only change is one variable.

Done when: you can put the two numbers side by side — 60 and 9 — and point at the one line of code that is different.

Why does the fixed version still end on minus lives?

Teacher reveal — why the cool-down must be its own script


when I receive [cool down v]
set [ghost v] effect to (55)
wait (0.4) seconds
clear graphic effects
set [hurt v] to (0)

CHALLENGE 3 · L3-22-M3🪙 70 Adcoins10 min

The stale round

Move your resets under the green flag, play two rounds, and watch the second one start already broken.

set [lives v] to (3) under the flag, not in the round.
Two rounds back to back, with two hits each.
Write down what round two started with.

WHAT IT SHOULD LOOK LIKE

Challenge 3 — the reset put under the green flag instead of at the start of a round. Round two begins on whatever round one left behind.

round 1 ends on 1 life

round 2 begins on 1 life

panels run left to right

Runs here in the page. Nothing to install.

How to use this: Click the green flag and read the speech bubbles. Two rounds run one after the other.

Round 1 ends on 1 life. Round 2 therefore BEGINS on 1 life and ends on −1.

Done when: you can state the rule in your own words, and point at each of your own resets and say which script it belongs in.

Teacher reveal — the rule

A reset belongs in the script that owns the thing being reset.

Under the flag: things that should outlast a round — the high score, the number of rounds played, the difficulty setting.
At the start of a round: things the round owns — lives, score, position, effects, leftover clones.

Ask them to list every variable in their project under one of those two headings. It takes four minutes and prevents most of the bugs in the next three arcs.

EXTRA MISSION · L3-22-MX🪙 100 Adcoinsbonus

Rounds done right

Three rounds in a row, each one starting clean, and a best score that survives all three.

The flag sets up only what outlasts a round.
The round resets only what it owns.
A best that never goes down.

Runs here in the page. Nothing to install.

How to use this: Click the green flag and let three rounds play out. Watch best against stars.

Three rounds, each clean, and a best of 23 that no later round could wipe.

Teacher note

Summary 5 min

touching (Bolt v)? plus set [state v] to [over] is a game you can lose.
A collision is tested every frame, so one touch is many hits unless you stop it.
The ghost effect does not make you safe. A hurt flag does — 60 touches became 9.
The cool-down goes in a script of its own, or the wait freezes the game.
A reset belongs in the script that owns the thing: the flag for what outlasts a round, the round for what it owns.

Lives: How many hits are left before the round ends.
Cool-down: A short time after an event during which it cannot happen again.
Flag variable: A variable holding 0 or 1, used as a yes-or-no answer.
Stale state: A new round starting on the last round’s leftovers.

Hand in

Save your game. Next lesson is the one that tests whether your state machine really works: pause.