Muffin Catcher IV

Review — where we got to 5 min

Your stall counts, ends, has sounds, and holds things worth different amounts.

• Falling clones, caught or landed.
• score up on one path, lives down on the other.
• A beetle that costs you, and a sound for every moment.

Quick-fire

Play your game for two minutes without missing. Is minute two any harder than minute one?

Today’s Topic 3 min

• A variable inside a block: wait (speed) seconds
• Keeping a changing number inside sensible limits
• switch backdrop to [Stars v] as the two states of a game
• broadcast [start v] from two different places

Learning outcome

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

1. Make a game speed up as the score rises, without it becoming impossible.
2. Show a game-over screen that is clearly not the game.
3. Start a fresh game from a button, with everything reset.

Learnt — speed, state, and a message 27 min

1 · A number can go inside a block

Your maker stack says wait (1) seconds. That 1 is the reason minute two is no harder than minute one.

Drag the variable (speed) into that white circle instead. The block now waits for whatever the box says, and you can change the box mid-game.

forever
  wait (1) seconds
  create clone of [myself v]
end
              

forever
  wait (speed) seconds
  create clone of [myself v]
end
              

Making it creep

Every catch takes a little off the wait. Put this on the caught path, next to the score block.

if <touching [Bowl v]?> then
  play sound [Pop v]
  change [score v] by (1)
  if <(speed) > (0.35)> then
    change [speed v] by (-0.05)
  end
  delete this clone
end
            

2 · The backdrop says which state the game is in

Right now your game just stops. The stall looks exactly as it did a second earlier, only nothing is falling. That is a game that has crashed, as far as the player can tell.

Give the ending its own backdrop. In this game the stall closes for the night, so Stars does the job.

when I receive [start v]
wait until <(lives) = (0)>
broadcast [game over v]
switch backdrop to [Stars v]
say (join [Game over! You caught ] (score))
            

Every muffin listens for that message and clears itself away, clones and all.

when I receive [game over v]
delete this clone
            

3 · One message, two senders

The last piece is a button that starts a new game. It works because of a change you have already half made: nothing starts on the green flag any more. Everything starts on a message.

1. On every sprite, swap when flag clicked for when I receive [start v].
2. Leave one when flag clicked in the whole project, on the Bowl.
3. That one resets the numbers, sets the backdrop, and then broadcast [start v].
4. Play. Nothing should look any different yet.

when flag clicked
set [score v] to (0)
set [lives v] to (3)
set [speed v] to (1)
switch backdrop to [Colorful City v]
broadcast [start v]
            

Now the button can send the same message, and the whole game starts again with no flag involved.

when I receive [start v]
hide

when I receive [game over v]
go to x: (0) y: (0)
show

when this sprite clicked
hide
set [score v] to (0)
set [lives v] to (3)
set [speed v] to (1)
switch backdrop to [Colorful City v]
broadcast [start v]
            

Basic — finish the game 25 min

Open your stall. This is the last time you build on it, so test after every step and save when it works.

Step 1 — a speed to change

1. Make a variable called speed. Untick it: nobody needs to see it.
2. Set it to 1 under the flag hat, with the other two.
3. Drag (speed) into the wait in every maker stack.
4. Play. It should feel exactly as it did before.

Step 2 — make it creep

1. Add the limit-and-change pair to the caught path of your everyday muffin.
2. Catch fifteen on purpose. It should be noticeably busier.
3. Catch fifty. It should be hard, not impossible.

Step 3 — the ending screen

1. Add the Stars backdrop to your project.
2. Build the referee stack on the Bowl, with the switch and the broadcast.
3. Add when I receive [game over v] and delete this clone to every falling sprite.
4. Lose on purpose. The sky should change and the stall should empty.

Step 4 — start on a message

1. Change every when flag clicked to when I receive [start v], except the one on the Bowl.
2. Make the Bowl’s flag stack the five-block one from the Learnt section.
3. Play. Everything should work exactly as before.

Step 5 — the button

1. Add a sprite for the button. A Bell, a Button, or your own drawing.
2. Build its three stacks.
3. Lose, click the button, and play a second game without touching the flag.

Step 6 — save it

1. Give the project a real name.
2. File → Save to your computer.
3. Close the tab, reopen Scratch, load the file and play it once.

Harder as you win

Make your game speed up as the player does well — and stay playable when they do.

• The first thirty seconds are gentle.
• After twenty catches it is clearly busier.
• However well somebody plays, it never becomes impossible or freezes.

An ending that looks like an ending

When the last life goes, the game should change into something a player can see is over.

• A different backdrop.
• Nothing left falling, and no leftover clones.
• The final score, said or shown.

Play again

Put a button on the ending screen. Clicking it should give a completely fresh game, with no green flag anywhere near it.

• The button only exists on the ending screen.
• A new game starts with a full three lives, a score of zero, and the gentle speed.
• You can play five games in a row without touching the flag.

A best score worth beating

Add one more number: best. It is the only thing in your project that does not go back to zero.

• best shows on the Stage all the time.
• It only changes when somebody beats it.
• A new record gets a different message from an ordinary game over.
• Starting a new game never resets it.

when I receive [start v]
wait until <(lives) = (0)>
broadcast [game over v]
switch backdrop to [Stars v]
if <(score) > (best)> then
  set [best v] to (score)
  say (join [Rekod baru! ] (score))
else
  say (join [Game over! You caught ] (score))
end
            

Summary 4 min

Four lessons, one game, and today it got a shape.

1. A variable can sit inside a block. wait (speed) seconds is what lets a game get harder while you play it.
2. Any number that keeps changing needs a limit, or it will run away.
3. The backdrop is a state. Open stall, closed stall, and the player can see which.
4. Starting on a message rather than the flag is what makes a second game possible.

Difficulty curve

A game that gets harder as the player gets better. Here it is one shrinking wait.

Game state

Which part of the game you are in — playing, or over. The backdrop shows it.

broadcast

A message every sprite can hear. Two different senders can send the same one.

Best score

A number that survives the reset, because it belongs to the player and not the game.

Next lesson: a new arc, and a project with no score in it at all. You make a music video.