Paddle Bounce I

Review — where we got to 5 min

Jump Dash is finished and shared. Two of its ideas come with us.

• A controller: forever with an if <key [right arrow v] pressed?> then inside it.
• A title screen and a button, which this game will get in three weeks.

Quick-fire

The hare hopped when you pressed a key. What will the ball do if you press nothing at all?

Today’s Topic 3 min

• move (6) steps and if on edge, bounce in a forever loop
• Direction, and why 90 and 0 are not the same kind of thing
• A paddle that only moves along one line
• A bounce off the paddle that you choose, not the edge

Learning outcome

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

1. Send a ball round the Stage for ever without it stopping.
2. Steer a paddle left and right along the bottom.
3. Bounce the ball off the paddle in a direction you decide.

Learnt — a ball, a paddle, a bounce 27 min

1 · A ball that never stops

Two blocks in a forever loop is the whole ball. Everything else in this arc hangs off those two.

1. New project, cat deleted, the Neon Tunnel backdrop.
2. Add the Ball sprite. Set its size to 70.
3. Start it in the middle with go to x: (0) y: (0).
4. Point it somewhere with point in direction (pick random (45) to (135)).
5. Add forever holding move (6) steps and if on edge, bounce.
6. Press the flag and watch it for a minute.

when flag clicked
go to x: (0) y: (0)
point in direction (pick random (45) to (135))
forever
  move (6) steps
  if on edge, bounce
end
            

2 · A paddle on a line

The paddle is a controller you have built four times now. The only new thing is that its up and down is missing on purpose.

1. Add the Paddle sprite.
2. Put it on its line: go to x: (0) y: (-140).
3. Build a forever with two ifs in it, for left and right.
4. Add if on edge, bounce so it cannot leave the Stage.
5. Press the flag, click the Stage, and slide it about.

when flag clicked
set rotation style [don't rotate v]
go to x: (0) y: (-140)
forever
  if <key [left arrow v] pressed?> then
    change x by (-12)
  end
  if <key [right arrow v] pressed?> then
    change x by (12)
  end
  if on edge, bounce
end
            

3 · The bounce you choose

A wall bounce is decided by the wall. A paddle bounce is decided by you, and that is where the game lives.

1. Go back to the ball and open its forever loop.
2. Add if <touching [Paddle v]?> then under the bounce.
3. Inside it, point somewhere upward: point in direction (pick random (-45) to (45)).
4. Then move (12) steps, to get clear of the paddle.
5. Play. Keep it up for as long as you can.

forever
  move (6) steps
  if on edge, bounce
  if <touching [Paddle v]?> then
    start sound [Boing v]
    point in direction (pick random (-45) to (45))
    move (12) steps
  end
end
            

Basic — build the rally 25 min

Build the ball first. A paddle with nothing to hit is not worth testing.

Step 1 — the ball

1. New project, cat deleted, a dark backdrop.
2. Add the ball, shrink it, and start it in the middle.
3. Build the move-and-bounce loop.
4. Watch it for a whole minute. It must never stop.

Step 2 — the paddle

1. Add the paddle and put it on its line.
2. Set its rotation style before anything else.
3. Build the two ifs and test both keys.

Step 3 — the bounce

1. Add the touching question inside the ball’s loop.
2. Point it upward and move it clear.
3. Play for a minute and count how many bounces you get.

Step 4 — tune it

1. Too fast to hit? Take the ball down to 4 steps.
2. Too easy? Take it up to 9.
3. Change one number, play, then change the next.

Step 5 — the sound

1. Give the paddle bounce a sound and the wall bounce a different one.
2. Close your eyes and listen to a rally. You should be able to follow it.

Your court

Pick a place for this game, and make sure the ball can be seen in it.

• A backdrop you chose.
• A ball you can follow across every part of it.
• A paddle that looks like it belongs to the same game.

A ball that never gets stuck

There are two ways this ball stops being a game. Find them both, then make sure neither can happen.

• The ball never ends up travelling flat along a wall.
• The ball never sits on the paddle shaking.
• You leave the game running for two minutes to prove it.

Twenty bounces worth watching

Count your bounces and get to twenty. Then look at what those twenty bounces actually looked like.

• A counter on the Stage that goes up on every paddle bounce.
• Twenty in one rally.
• No two bounces sent the ball to the same place.

Two balls, one paddle

One ball is a rally. Two is a decision, every second, about which one you can still reach.

• Two balls on the Stage, both bouncing properly.
• They start in different places, going different ways.
• Both bounce off the paddle.
• They can pass each other without getting stuck together.

Summary 4 min

A game that runs on its own, and a player who has to keep up with it.

1. move (6) steps plus if on edge, bounce in a forever loop is a ball.
2. Direction counts clockwise from straight up: 0 is up, 90 is right.
3. The paddle moves along one line and never changes its y.
4. After a paddle bounce, move the ball clear or it bounces again.

Direction

Which way a sprite faces. 0 up, 90 right, 180 down, −90 left.

Bounce

Turning the ball round. The wall decides one; you decide the other.

Rally

A run of bounces with no miss in it.

Rotation style

Whether a sprite is allowed to turn. A paddle is not.

Next lesson: the floor stops being friendly, and missing starts to cost something.