Whack-a-mole Game IV

Review — where we got to 5 min

Last lesson your game learnt to finish and start again.

• round () and join () () turn a long sum into “87%”.
• Everything starts on when I receive [Play v], so a Retry button can start it too.
• delete this clone on Over, or the next round runs on top of the last.

Quick-fire

Your accuracy comes out as 260%. What has gone wrong?

Today’s Topic 3 min

• A cheat that is hiding in your game right now
• Two costumes, and hitting by colour
• Digits that keep up with a changing number
• My Blocks — making a block of your own

Learning outcome

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

1. Find a cheat in your own game and close it.
2. Show a changing variable in your own digits.
3. Turn repeated code into one custom block with inputs.

Learnt — fair, and tidy 28 min

Try to cheat your own game

Open last lesson’s game. Press the mouse button down and keep it down, then drag the hammer slowly across every mole on the board.

You score every one of them. And your hit count only went up by one.

Look at why. The mole was told:

if <<touching [Hammer v]?> and <mouse down?>> then
  change [score v] by (1)
end
            

The fix: hit by colour

Give the hammer two costumes. They are identical apart from the striking edge:

1. Costume hammer — the edge painted black.
2. Costume hit — the same hammer, edge painted blue.

Now the mole stops watching the hammer and watches the blue:

if <touching color [#003FFF]?> then
  change [score v] by (1)
  delete this clone
end
            

And the hammer only wears the blue edge for a moment, once per press:

when I receive [Play v]
switch costume to [hammer v]
forever
  if <mouse down?> then
    switch costume to [hit v]
    change [hit v] by (1)
    wait (0.15) seconds
    switch costume to [hammer v]
    wait until <not <mouse down?>>
  end
end
            

Digits that keep up

Last lesson your digits showed the accuracy — a number worked out once, at the end. Score, hit and time are different. They change all through the game.

So the same blocks go inside a forever loop, and every clone deletes itself after 0.03 seconds.

when I start as a clone
go to [front v] layer
show
wait (0.03) seconds
delete this clone
            

Three readouts, three near-identical scripts

Look at what the digit sprite has to say for score, for hit, and for time:

Only four things change between them:

1. the variable
2. the ones-digit x
3. the tens-digit x
4. the y

Everything else is copied out three times. Add a fourth readout and you copy it a fourth time. Change your mind about how the digits work and you fix it in three places, and miss one.

My Blocks — a block you write yourself

In the block palette, at the very bottom, is My Blocks. Click Make a Block.

1. Type a name: “Show Digits”.
2. Click Add an input four times — one for each thing that changes.
3. Name them: num, ones x, tens x, y.
4. Click OK. A define hat appears in your scripts.

Drag one of your three scripts under the define hat — just one — then drag the orange ovals from the hat into the places where the values used to be.

define Show Digits (num) (ones x) (tens x) (y)
if <(num) < (10)> then
  switch costume to (letter (1) of (num))
  go to x: (ones x) y: (y)
  create clone of [myself v]
else
  switch costume to (letter (1) of (num))
  go to x: (tens x) y: (y)
  create clone of [myself v]
  switch costume to (letter (2) of (num))
  go to x: (ones x) y: (y)
  create clone of [myself v]
end
            

Now the whole forever loop is three lines:

forever
  Show Digits (score) (-79) (-94) (155) :: custom
  Show Digits (hit) (35) (20) (-145) :: custom
  Show Digits (time) (140) (125) (155) :: custom
end
            

Basic — make the hammer fair 24 min

Open your Lesson 3 game.

Step 1 — prove the bug

Play a round holding the mouse button down the whole time. Write down your accuracy. It should be silly.

Step 2 — the second costume

Right-click your hammer costume and choose duplicate. Rename the copy hit. Paint its striking edge blue, and make sure the first costume’s edge is black.

Step 3 — the hammer’s new script

Replace the point in direction (90) swing with the costume swap: switch to hit, change hit by 1, wait 0.15, switch back, wait until the button is up.

Step 4 — the mole watches the colour

In the mole’s clone script, change <touching [Hammer v]?> and <mouse down?> to touching color [ ]? and eyedrop the blue off your hammer.

Step 5 — try to cheat again

Hold the button down and sweep. Nothing should happen. Then click properly and score.

No more cheating

One swing can score one point at most. Prove it to yourself.

• Hold the mouse down and sweep the whole board — the score must not move.
• Click properly on a mole — the score must go up by one.
• Your accuracy can never be more than 100%.

Your digits, everywhere

The deck’s mission, first half. Turn off every grey monitor.

• Score, hit and time all shown in your own digits.
• Each one in its own corner, and each one keeping up as it changes.
• No flickering.

Write your own block

The deck’s mission, second half. The game must not change — only the code.

• Make a My Block called Show Digits with four inputs.
• Move the digit code into it, once.
• Call it three times: score, hit, time.
• Play the game. It should look and feel exactly as it did before.

Build the whole menu

This is the big one, and the reward says so. Give your game a proper menu, and let the player set up the round before it starts.

• Board: 3×3, 4×4 or 5×5 holes
• Clock: 30, 60 or 90 seconds
• Difficulty: easy, medium or hard

Summary 5 min

• Blocks can be exactly right and still say the wrong thing. mouse down? means “held”, not “pressed”.
• Two costumes that differ in one colour let touching color [ ]? tell a swing from a hold.
• A number that changes needs its digits made in a forever loop, with each clone lasting 0.03 seconds.
• My Blocks let you name a job once and ask for it by name. Every programming language has this.
• When you find yourself copying blocks for the third time, make a block instead.

My Block

A block you make yourself. Everywhere else it is called a function.

Input

A hole in your block. You fill it in when you use the block.

touching color

True when the sprite is touching that exact colour anywhere on screen.

Cheat

A way to win that the game never meant to allow.

Hand in

Share your finished Whack-a-mole and send the link to your teacher. That is the arc complete — next lesson starts the Car Race.