Muffin Catcher II

Review — where we got to 5 min

Last lesson you built a stall where muffins fall and a bowl catches them.

• A clone starts at the top, at a random x.
• It comes down inside a repeat (10), ten pixels at a time.
• It deletes itself two ways: caught by the bowl, or landed on the ground.

Quick-fire

You play for a minute and catch loads of muffins. What does the game know about that?

Today’s Topic 3 min

• Two variables in one game — score and lives
• change [score v] by (1) on the caught path
• change [lives v] by (-1) on the missed path
• if <(lives) = (0)> then and stop [all v]

Learning outcome

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

1. Make two variables and reset both when the flag is clicked.
2. Add to one and take from the other, in the right two places.
3. End the game when a number runs out, and say how the player did.

Learnt — winning, losing, and the two paths 27 min

A game needs two things your stall has not got. Something to try for, and something to lose. Both are numbers, and you already know the block that makes one.

Two boxes, not one

A variable is a box with a name on it, from Topic 1.11. This game needs two of them, and they behave in opposite ways.

The two paths were already there

Look at last lesson’s falling stack. It has two delete this clone blocks, and they mean different things. One is a catch. One is a miss.

That is where the two numbers go. Nothing else in the stack changes.

when I start as a clone
show
go to x: (pick random (-200) to (200)) y: (170)
repeat (34)
  change y by (-10)
  if <touching [Bowl v]?> then
    change [score v] by (1)
    delete this clone
  end
end
change [lives v] by (-1)
delete this clone
            

Resetting, and why it matters

Both boxes need setting when the flag is clicked. Without that, your second game starts with your first game’s score, and with zero lives.

1. Open Variables and click Make a Variable. Name it score.
2. Make a second one called lives.
3. Tick both boxes in the palette so they show on the Stage.
4. On the Bowl, under when flag clicked, add set [score v] to (0).
5. Add set [lives v] to (3) under it.
6. Click the flag twice. Both numbers should jump back to 0 and 3.

The ending

A game with no ending is not a game. When lives reaches 0, everything should stop.

when flag clicked
set [score v] to (0)
set [lives v] to (3)
wait until <(lives) = (0)>
say (join [Game over! You caught ] (score))
stop [all v]
            

wait until <> is a Control block that sits and waits for a question to become true. (join [] []) from Operators glues a sentence and a number together so the bowl can say both.

Use the plain say [Hello!] here, not the one with seconds on it. A timed say holds the script for three seconds before the stop, and in those three seconds more muffins land and lives drops to −2. With the plain one the stop is instant, and the bubble stays on screen anyway, because stopping does not clear a bubble.

Basic — make it count 25 min

Open your stall from last lesson. Build in this order and test after every step.

Step 1 — two boxes

1. Make the variables score and lives.
2. Tick both so they show on the Stage.
3. Drag the monitors to a corner where no muffin will land on them.

Step 2 — reset them

1. On the Bowl, add the two set blocks under the flag hat.
2. Click the flag. Check both numbers change to 0 and 3.

Step 3 — count the catches

1. On the muffin, put change [score v] by (1) inside the touching-if, above the delete.
2. Play. Every catch should add exactly one.
3. If it jumps by two, you have the block in two sprites, or twice in one.

Step 4 — count the misses

1. Put change [lives v] by (-1) below the repeat, above the last delete.
2. Let a muffin land. Lives should go from 3 to 2.
3. Catch one. Lives should not move.

Step 5 — the ending

1. Add the waiting stack from the Learnt section to the Bowl.
2. Let three muffins land on purpose.
3. The bowl should announce your score, and everything should stop.

Step 6 — play it twice

1. Press the flag again after a game over.
2. Score 0, lives 3, muffins falling. If not, a reset is missing.

Score your own stall

Take the game you made for last lesson’s Challenge 1 — your own catcher, your own falling things — and make it count.

• Every kind of falling thing adds to the same score.
• The score is visible while you play.
• It is back to 0 on every green flag.

Three misses and you are out

Now make it possible to lose. Three lives, shown on the Stage, gone one at a time.

• A miss costs a life. A catch never does.
• At zero, the game says something and stops.
• The message includes the score.

A game you can win

Losing is only half of it. Give your stall a target — twenty muffin, say — and a different ending when the player reaches it.

• Two endings, and they say different things.
• Whichever comes first ends the game.
• Neither ending can happen twice in one run.

when flag clicked
wait until <(lives) = (0)>
say (join [Game over! You caught ] (score))
stop [all v]

when flag clicked
wait until <(score) > (19)>
say [Menang! Twenty muffin.]
stop [all v]
            

The star that gives a life back

Once in a while, something falls that is worth more than points. Catch it and you get a miss back.

• It falls much less often than the muffins do.
• Catching it adds a life, not a point.
• Lives never go above three, however many stars you catch.
• Missing a star costs nothing.

if <touching [Bowl v]?> then
  if <(lives) < (3)> then
    change [lives v] by (1)
  end
  delete this clone
end
            

Summary 4 min

A game needs a reason to play and a way to lose. Both are numbers.

1. score starts at 0 and goes up on the caught path.
2. lives starts at 3 and goes down on the missed path.
3. wait until <(lives) = (0)> sits quietly until the game is over, then ends it.

You did not change how the muffins fall. You added two blocks to a stack you already had, in the two places it already forked.

Lives

A number that counts down. When it reaches zero the game ends.

wait until

A Control block that holds a script until a question becomes true.

join

An Operators block that glues two things into one, so a sprite can say both.

Game over

An ending the game reaches by itself, with a message and a stop.

Next lesson: not every muffin is worth the same, and one of them you must not catch at all.