Whack-a-mole Game III

Review — where we got to 5 min

Last lesson the board got busy and the game got fussy.

• One spawner stack per hole, so several moles are up at once.
• wait until <not <mouse down?>> makes one press count once.
• Accuracy is ((score) / (hit)) * (100), and <> and <> needs both halves true.

Quick-fire

You scored 41 from 47 swings. What does the accuracy sum give you?

Today’s Topic 3 min

• Showing a result the player can read
• The order things happen in when a game ends
• A Retry button, and why the green flag has to step aside
• Clearing up your clones
• Numbers drawn in your own digits

Learning outcome

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

1. Round a number and join words onto it.
2. Start a whole game from a broadcast so anything can restart it.
3. Delete leftover clones so a second round is as fast as the first.

Learnt — finishing properly 27 min

A number a person can read

round () throws the decimals away. join () () sticks two things together. Together they turn 88.888888 into 89%.

set [accuracy v] to (join (round (((score) / (hit)) * (100))) [%])
            

One thing at a time

The end of a round is a little sequence, and each step calls the next:

1. The clock reaches zero.
2. Broadcast Over — everything stops making moles.
3. The verdict appears: you win, or you lose.
4. Broadcast Statistic — the accuracy box shows the number.
5. Broadcast Retry — the button appears.

Do it all at once and the box lands on top of the verdict. Broadcasts are how you make things queue up.

Why the green flag has to step aside

You want a Retry button. But a button cannot press the green flag — nothing in Scratch can.

So the flag stops being the thing that starts the game. It shouts a word instead, and everything listens for the word:

when flag clicked
broadcast [Play v]
            

Every other when flag clicked in your game — hammer, holes, moles, referee, everything — becomes when I receive [Play v].

And now the Retry button is three blocks, because it can shout the same word:

when this sprite clicked
broadcast [Play v]
            

Clear up your clones

Here is a bug that only shows up on the third go. Every round makes moles; if the old ones are never deleted, they keep running underneath the new ones.

Round one is fine. Round three has three rounds’ worth of moles all popping up, and your computer starts to struggle.

when I receive [Over v]
delete this clone
            

Numbers in your own digits

Scratch’s monitor is a grey box that does not match your game. You can draw your own numbers instead.

Make one sprite with eleven costumes: 0, 1, 2 … 9 and %. Name each costume after what it shows — the costume for eight is called 8.

Then letter (1) of (accuracy) gives you the first character of “87%”, which is “8” — and that is the name of a costume.

switch costume to (letter (1) of (accuracy))
go to x: (-30) y: (0)
create clone of [myself v]
switch costume to (letter (2) of (accuracy))
go to x: (30) y: (0)
create clone of [myself v]
            

Basic — make it restartable 25 min

Open your Lesson 2 game. Nothing about the playing changes; everything about the starting does.

Step 1 — the accuracy variable

Make a variable called accuracy. Set it to nothing at the start of a round.

Step 2 — the box

Add a sprite for the result box, hidden at the start. Give it a when I receive [Statistic v] stack that works out the accuracy with round and join, goes to the front, and shows it.

Step 3 — the sequence

On the referee: after the verdict, broadcast [Statistic v]. Take out the stop [all v] — the round is not over until the button is up.

Step 4 — Play instead of the flag

Change every when flag clicked in your project to when I receive [Play v]. Then add one new stack, anywhere: when flag clicked then broadcast [Play v].

Test now. The game should behave exactly as it did before.

Step 5 — the Retry button

Add a button sprite, hidden at the start. It shows on when I receive [Retry v], and its when this sprite clicked stack broadcasts Play.

Step 6 — clear up

Give the mole and the hole a when I receive [Over v] stack with delete this clone.

Step 7 — play five rounds

Click Retry five times in a row. The fifth round must feel exactly like the first. If it is slower, a clone is not being deleted.

Show the accuracy

At the end of every round — win or lose — show the player how accurate they were.

• A whole number, not a long decimal.
• With a % after it.
• After the verdict, not on top of it.

Play again

• Every start block becomes when I receive [Play v].
• A Retry button appears at the end and starts a fresh round when clicked.
• Every clone is deleted when the round ends.

Your own digits

The deck’s mission. Stop using Scratch’s grey monitor for the result.

• Paint one sprite with costumes 0–9 and %, each named after what it shows.
• Show the accuracy in those digits at the end of the round.
• It must look right at 9%, 87% and 100% — two, three and four characters.
• Show the score the same way.

if <(accuracy) < (10)> then
  say [two characters: the digit and the %]
else
  if <(accuracy) < (100)> then
    say [three characters]
  else
    say [four characters]
  end
end
            

A title screen

You have already done the hard part. Everything starts on Play — so nothing has to start when the flag is clicked.

Give your game a proper front page: a title, and a button. The flag shows the title screen and waits. The game begins only when the player says so.

Summary 5 min

• round () drops the decimals; join () () sticks things together. Together they make a result readable.
• The end of a game is a sequence. Each step broadcasts the next, so things happen one at a time.
• Move every start onto when I receive [Play v] and the flag becomes just one of the things that can start the game.
• Delete your clones when a round ends, or the next round runs on top of the last one.
• letter (1) of (accuracy) picks one character, and a costume named after that character can be chosen with it.

round

Turns 88.888 into 89 — the nearest whole number.

join

Sticks two pieces of text together. The result is text, not a number.

Sequence

Things happening one after another, each one calling the next.

Clean-up

Deleting what a round left behind, so the next round starts fresh.

Hand in

Share your project and send the link to your teacher. Next lesson finishes Whack-a-mole.