Bubble Popper III

Review — last lesson 5 min

• For all sprites is one box for the project; for this sprite only is one box per clone.
• A crowd moving in lockstep means a shared variable.
• A clone inherits the sprite’s position, size, costume and sprite-only values.

Quick-fire

Your reef has twenty bubbles rising at their own speeds. You want a score. Is score shared, or for this sprite only?

Today’s Topic 3 min

• when this sprite clicked on a clone — it runs on the one you hit
• Deleting the clicked clone, and only that one
• Points that belong to the bubble, added to a score that belongs to the game
• A streak, and a rare bubble worth ten

Learning outcome

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

1. Make a clone respond to being clicked.
2. Score a click by what that particular clone was worth.
3. Say why a shared worth gives a wrong score that looks plausible.

Learnt — the click finds the clone 28 min

1 · A hat that clones do run

Clones ignore when flag clicked. They do not ignore these:

• when this sprite clicked
• when [space v] key pressed
• when I receive [message1 v]

The click one is special: Scratch works out which clone was under the pointer and runs that clone’s script. Its nineteen neighbours carry on rising and never hear about it.

when this sprite clicked
change [popped v] by (1)
delete this clone
            

2 · Points that belong to the bubble

A game where every bubble is worth 1 is dull. Make the small fast ones valuable and the big slow ones cheap — which needs each clone to carry its own worth.

Three sprite-only variables, all set in the spawner before the clone is made:

set [my size v] to (pick random (20) to (64))
set [speed v] to (round ((9) - ((my size) / (12))))
set [worth v] to (round ((8) - ((my size) / (10))))
create clone of [myself v]
            

3 · Shared plus sprite-only, in one line

when this sprite clicked
change [popped v] by (1)
change [score v] by (worth)
delete this clone
            

Basic — the popping game 24 min

Open last lesson’s shoal. You are turning it into something you can play.

Step 1 — the shared score

1. Make score and popped, both for all sprites.
2. Set both to 0 under the green flag. Show both readouts.

Step 2 — the bubble’s own numbers

1. Make my size and worth, for this sprite only. You already have speed.
2. In the spawner, roll my size from 18 to 62.
3. Work speed out from it, and worth too — both wrapped in round.

Step 3 — the clone uses them

1. In the clone script: set size to (my size) %.
2. Rise using speed as before, then delete.

Step 4 — the pop

1. Add when this sprite clicked to the Bubble.
2. Inside: change [popped v] by (1), then change [score v] by (worth).
3. Finish with delete this clone.

Step 5 — the result card

1. After the spawner’s loop, wait a couple of seconds for the last bubbles to clear.
2. Bring the original back to the middle, show it, and say the two totals joined together.
3. hide it again so it is not sitting there next run.

when flag clicked
hide
set [score v] to (0)
set [popped v] to (0)
repeat (26)
  go to x: (pick random (-175) to (175)) y: (-170)
  set [my size v] to (pick random (18) to (62))
  set [speed v] to (round ((9) - ((my size) / (12))))
  set [worth v] to (round ((8) - ((my size) / (10))))
  switch costume to (pick random (1) to (5))
  create clone of [myself v]
  wait (0.24) seconds
end
wait (2.5) seconds
go to x: (0) y: (0)
show
say (join (popped) (join [ popped for ] (score))) for (3) seconds
hide
            

The wrong score

Make worth shared instead, and see what a plausible-looking wrong score feels like.

• The worth readout is visible and changes constantly.
• You pop a tiny bubble and score whatever the newest one is worth.
• Write down why nobody playing would notice.

Combo

Reward accuracy. Pops in a row are worth more; letting one escape costs the streak.

• A shared streak that goes up on every pop.
• The score rises by worth × streak.
• A bubble reaching the surface sets the streak back to 0.
• A best streak that remembers the run’s high point.

repeat until <(y position) > (165)>
  change y by (speed)
end
set [streak v] to (0)
delete this clone
            

Golden bubbles

About one bubble in eight is golden: smaller, brighter, and worth ten of the others.

• A sprite-only golden that is 1 or 0, decided in the spawner.
• A golden bubble looks unmistakably different, and is worth 10.
• A counter of how many golden ones the run produced.

when I start as a clone
show
if <(golden) = (1)> then
  switch costume to [yellow v]
  set size to (34) %
  set [brightness v] effect to (40)
else
  switch costume to [blue v]
  set size to (48) %
  clear graphic effects
end
            

A pop you can see

At the moment a bubble just disappears. Make it burst: grow, fade, and only then delete itself.

• The clicked bubble grows and fades over a handful of steps.
• The other bubbles are completely unaffected while it does.
• The score goes up straight away, not after the animation.

Summary 5 min

• when this sprite clicked runs on the clone you actually hit.
• delete this clone removes that one clone, not the rest.
• Score and streak are shared; worth, size and speed belong to the bubble. One line often uses both.
• A shared worth gives a wrong score that still looks like a working game.
• Wrap derived numbers in round or the player sees decimals.

Hit test

Scratch working out which clone the pointer was over.

Worth

What one particular bubble scores — sprite-only, always.

Streak

How many pops in a row without a miss.

Result card

The original sprite reappearing at the end to report the totals.

Hand in

Save your game. Next lesson it becomes a game you can lose — and the round ends by itself.