Boss Tower III

Review — Boss Tower II 5 min

• The dragon reads its next move with (item (step) of [pattern v]).
• A move is a list of spots. The Marker and the Fireball both read spots.
• A fair attack always leaves a gap.

Quick-fire

Arena Duel drew its health bars with eleven costumes, one for each tenth. How many would a dragon with 37 health need?

Today’s Topic 3 min

• A health bar drawn with the Pen
• A second phase at half health: a new pattern, faster
• A hit flash and a screen shake
• Win and lose

Learning outcome

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

1. Draw a bar whose length follows a variable.
2. Change how a sprite behaves when a number crosses a line.
3. Finish a game with two different endings.

Learnt — health, anger and an ending 28 min

1 · A health bar from one sum

You drew with the Pen in Sketch Pad. A health bar is two straight lines: a grey one for the whole bar, and a red one on top for the health left.

define draw bar
erase all
set pen size to (12)
set pen color to [#3A3A3A]
go to x: (-100) y: (160)
pen down
go to x: (100) y: (160)
pen up
if <(boss hp) > (0)> then
  set pen color to [#E0262B]
  go to x: (-100) y: (160)
  pen down
  go to x: ((-100) + ((200) * ((boss hp) / (max hp)))) y: (160)
  pen up
end

when flag clicked
hide
forever
  draw bar :: custom
end
            

2 · Phase 2 at half health

First, swap two numbers in the dragon’s brain for variables: rest (1.2) and wind-up (1). Then one more script can change how the whole fight feels.

glide (rest) secs to x: (pick random (-150) to (150)) y: (70)
wait (wind-up) seconds
wait (rest) seconds
              

when flag clicked
wait (0.1) seconds
wait until <not <(boss hp) > ((max hp) / (2))>>
delete all of [pattern v]
add [rain] to [pattern v]
add [sweep] to [pattern v]
add [rain] to [pattern v]
set [step v] to (1)
set [wind-up v] to (0.6)
set [rest v] to (0.8)
set [color v] effect to (150)
say [ROAR!] for (1) seconds
              

The new pattern and the new wind-up are still fair: rain still has its gap, and 0.6 seconds is still longer than a person needs to react.

3 · A flash and a shake

A hit has to feel like a hit. When a bolt lands, it broadcasts two messages.

when I receive [hurt v]
start sound [Clang v]
set [brightness v] effect to (70)
wait (0.1) seconds
set [brightness v] effect to (0)
              

when I receive [shake v]
repeat (3)
  change x by (6)
  wait (0.03) seconds
  change x by (-6)
  wait (0.03) seconds
end
              

4 · Two endings

A referee on the Knight waits for either number to run out, then says which ending it is.

when flag clicked
set [state v] to [fight]
wait (0.1) seconds
wait until <<(boss hp) < (1)> or <(lives) < (1)>>
if <(boss hp) < (1)> then
  set [state v] to [win]
  broadcast [win v]
else
  set [state v] to [lose]
  broadcast [lose v]
end
            

Basic — a fight with an ending 25 min

Open your boss fight from last lesson.

Step 1 — the numbers

1. New variables for all sprites: boss hp, max hp, lives, rest, wind-up and state.
2. On the Knight’s green flag: set [boss hp v] to (max hp) and set [lives v] to (3). Set max hp to 10.
3. On the Dragon’s green flag: set [rest v] to (1.2) and set [wind-up v] to (1), and put the three pattern items back into the list.

Step 2 — hits and burns

1. In the Bolt, a landed hit now does change [boss hp v] by (-1), broadcast [hurt v] and broadcast [shake v].
2. In the Fireball, a burn now does change [lives v] by (-1).

Step 3 — the bar and phase 2

1. Make a Bar sprite (any costume — it stays hidden). Build the bar from section 1.
2. Swap the three numbers in the brain, and add the phase 2 script, from section 2.
3. Add the flash and the shake from section 3.

Step 4 — the endings

1. Add the referee to the Knight, and wrap its keys in the state check.
2. Dragon, on win: stop its other scripts, fade out with the ghost effect, hide.
3. Knight, on win: stop its other scripts, play Win, say “Victory!”. On lose: play Lose, say “Burnt! Try again.”

when I receive [win v]
stop [other scripts in sprite v]
switch costume to [dragon-a v]
repeat (10)
  change [ghost v] effect by (10)
  change y by (-4)
end
hide

when I receive [lose v]
stop [other scripts in sprite v]
switch costume to [dragon-c v]
say [Too hot for you!]
            

A bar that warns you

• Above half health, the bar is green.
• Above a quarter, it is orange.
• At a quarter or less, it is red.

if <(boss hp) > ((max hp) / (2))> then
  set pen color to [#2EB82E]
else
  if <(boss hp) > ((max hp) / (4))> then
    set pen color to [#FF9F1A]
  else
    set pen color to [#E0262B]
  end
end
            

Hearts, stamped

Swap the lives number for pictures.

• Give the Bar sprite the Heart costume.
• One heart per life, in a row at the top left.
• Hide the lives monitor — the hearts say it now.

go to x: (-210) y: (160)
repeat (lives)
  show
  stamp
  hide
  change x by (28)
end
            

A damage trail

Show the player how much a hit took.

• When the dragon is hit, the part that was lost turns white.
• The white part then drains away smoothly, behind the red.
• It catches up in about a second.

when flag clicked
hide
set [shown hp v] to (10)
forever
  if <(shown hp) > (boss hp)> then
    change [shown hp v] by (-0.05)
  end
  draw bar :: custom
end
            

Phase 3: the bats

Give the fight a final phase.

• At a quarter health, the dragon calls two bats.
• The bats swoop back and forth over the knight’s head.
• A bat that touches the knight costs a life. A bolt pops a bat.
• The bats leave when the dragon is beaten.

when I receive [bats v]
set [my no v] to (0)
repeat (2)
  change [my no v] by (1)
  create clone of [myself v]
end

when I start as a clone
go to x: ((((my no) * (2)) - (3)) * (180)) y: (-20)
point in direction (((3) - ((my no) * (2))) * (90))
show
forever
  move (4) steps
  if on edge, bounce
  set y to ((-30) + ((30) * ([sin v] of ((timer) * (200)))))
  if <touching [Bolt v]?> then
    delete this clone
  end
  if <touching [Knight v]?> then
    change [lives v] by (-1)
    delete this clone
  end
end
            

Summary 5 min

• A Pen health bar is two lines, and the second one’s end is one sum.
• A boss gets a second phase when a number crosses a line: new list, shorter wind-up.
• A flash and a shake make a hit feel like a hit.
• A referee waits for either number to run out, and picks the ending.

Health bar

A line whose length shows how much health is left.

Threshold

The number at which something changes — here, half health.

Juice

Small effects that make an action feel strong: flashes, shakes, sounds.

Ending

What the game does when it is won or lost.

Hand in

Save your boss fight. Next lesson it gets its front and back doors: a title screen, the credits, and a best time to beat.