Arena Duel II

Review — two players, one keyboard 5 min

• Each fighter has its own loop and its own keys.
• walk is move-ask-undo on x and then on y.
• Two copies of the same code must stay the same — except where they must not.

Quick-fire

A fighter will fire orbs. How can a clone of an Orb sprite know where the fighter is and which way it is facing, when the fighter is a different sprite?

Today’s Topic 3 min

• Firing: create clone of (Orb 1 v) from another sprite
• An orb that flies until a wall, a pillar or an enemy
• health 1, health 2, and a bar with a costume per tenth
• A cooldown kept by the timer

Learning outcome

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

1. Fire clones from one sprite that belong to another.
2. Show a number as a picture — a health bar.
3. Limit how fast something can happen, using time rather than counting.

Learnt — firing 28 min

1 · An orb is a clone

Tera has its own Orb sprite, Orb 1, hidden. Firing is a My Block on Tera:

define fire
if <(timer) > (next shot)> then
  set [next shot v] to ((timer) + (0.4))
  set [shot 1 x v] to (x position)
  set [shot 1 y v] to (y position)
  set [shot 1 dir v] to (direction)
  create clone of (Orb 1 v)
end
            

when I start as a clone
go to x: (shot 1 x) y: (shot 1 y)
point in direction (shot 1 dir)
show
repeat until <touching color [#8B5A3C]?>
  move (8) steps
  if <touching (Giga v)?> then
    change [health 2 v] by (-10)
    delete this clone
  end
end
delete this clone
            

2 · A hit, and a health bar

The orb above already takes ten off health 2 when it touches Giga. To show it, a Bar sprite has eleven costumes — red 0 to red 10 — and wears the one that matches:

forever
  switch costume to (join [red ] (round ((health 2) / (10))))
end
            

Basic — the duel 24 min

Open your face-off and give both fighters something to fire.

Step 1 — the orbs

1. Draw a small round orb — blue for Tera, red for Giga — as two sprites, Orb 1 and Orb 2.
2. Both hidden when the flag is clicked.
3. Build Orb 1’s clone script from Learnt part 1; Orb 2’s is the same, reading shot 2 and hurting Tera.

Step 2 — fire

1. Make health 1, health 2 and the six shot variables, for all sprites. Set both healths to 100.
2. Give each fighter a next shot variable, for this sprite only, and the fire block.
3. Space fires for Tera; L fires for Giga.

Step 3 — the bars

1. Paint a bar with eleven costumes, from empty to full, on the same canvas.
2. One bar top-left for Tera, one top-right for Giga.

The own goal

Make Tera’s orb hurt any fighter it touches, and fire three at Giga. Count who gets hit.

• The orb checks for Tera as well as Giga.
• Keep a count of hits on each.
• Explain the result, then put it right.

A cooldown

Hold fire for two seconds, with and without a cooldown of 0.4 seconds.

• The cooldown uses (timer) and a next shot time.
• Count the orbs each way.

Cover

Fire four orbs at Giga hiding behind a pillar, then four more with Giga in the open.

• Nothing new to build — the orb already stops at the wall colour.
• Count hits behind the pillar and in the open.

Knockback

A hit should shove the fighter backwards — but never through a wall.

• The orb sets knocked 2 to 6 when it hits Giga.
• Giga’s loop: while knocked 2 is above 0, walk away and count it down.

Summary 5 min

• A fighter fires by leaving notes in variables and cloning its own Orb sprite.
• An orb flies until the wall colour, a pillar or the enemy, then deletes itself.
• A bar with a costume per tenth draws health as a picture.
• An orb must know who fired it, or it hits its own shooter.
• Cooldowns belong on the timer, not on a counter.

Projectile

Something fired that travels on its own — here, an orb.

Health bar

A picture that shows a number at a glance.

Cooldown

The wait before something can happen again.

Friendly fire

Being hit by your own side’s shot.

Hand in

Save your duel. Next lesson it becomes a match: rounds, a referee and a winner.