prog8/examples/balloonflight.p8

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%import syslib
%import textio
%import math
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%import test_stack
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%zeropage basicsafe
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; note: The flickering in the scrolling is caused by the CPU requiring
; too long to scroll the characters + the colors in course scroll.
; This takes nearly a full frame to accomplish, and causes tearing.
; It's very difficult to remove this flicker: it requires double buffering
; and splitting the coarse character scrolling on multiple phases...
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main {
ubyte perform_scroll = false
sub start() {
c64.SPRPTR[0] = $0f00 / 64
c64.SPENA = 1
c64.SP0COL = 14
c64.SPXY[0] = 80
c64.SPXY[1] = 100
c64.SCROLX &= %11110111 ; 38 column mode
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sys.set_rasterirq(&irq.irqhandler, 200, false) ; enable animation via raster interrupt
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ubyte target_height = 10
ubyte active_height = 24
bool upwards = true
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repeat {
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;txt.plot(0,0)
;test_stack.test()
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ubyte mountain = 223 ; slope upwards
if active_height < target_height {
active_height++
upwards = true
} else if active_height > target_height {
mountain = 233 ; slope downwards
active_height--
upwards = false
} else {
target_height = 8 + math.rnd() % 16
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if upwards
mountain = 233
else
mountain = 223
}
while not perform_scroll {
; let the raster irq do its timing job
}
perform_scroll = false
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txt.scroll_left(true)
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; float the balloon
if math.rnd() & %10000
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c64.SPXY[1] ++
else
c64.SPXY[1] --
ubyte yy
for yy in 0 to active_height-1 {
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txt.setcc(39, yy, 32, 2) ; clear top of screen
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}
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txt.setcc(39, active_height, mountain, 8) ; mountain edge
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for yy in active_height+1 to 24 {
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txt.setcc(39, yy, 160, 8) ; draw mountain
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}
yy = math.rnd()
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if yy > 100 {
; draw a star
txt.setcc(39, yy % (active_height-1), '.', math.rnd())
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}
if yy > 200 {
; draw a tree
ubyte tree = 30
ubyte treecolor = 5
if yy & %01000000 != 0
tree = 88
else if yy & %00100000 != 0
tree = 65
if math.rnd() > 130
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treecolor = 13
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txt.setcc(39, active_height, tree, treecolor)
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}
if yy > 235 {
; draw a camel
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txt.setcc(39, active_height, 94, 9)
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}
}
}
}
spritedata $0f00 {
; this memory block contains the sprite data
; it must start on an address aligned to 64 bytes.
%option force_output ; make sure the data in this block appears in the resulting program
ubyte[] balloonsprite = [ %00000000,%01111111,%00000000,
%00000001,%11111111,%11000000,
%00000011,%11111111,%11100000,
%00000011,%11100011,%11100000,
%00000111,%11011100,%11110000,
%00000111,%11011101,%11110000,
%00000111,%11011100,%11110000,
%00000011,%11100011,%11100000,
%00000011,%11111111,%11100000,
%00000011,%11111111,%11100000,
%00000010,%11111111,%10100000,
%00000001,%01111111,%01000000,
%00000001,%00111110,%01000000,
%00000000,%10011100,%10000000,
%00000000,%10011100,%10000000,
%00000000,%01001001,%00000000,
%00000000,%01001001,%00000000,
%00000000,%00111110,%00000000,
%00000000,%00111110,%00000000,
%00000000,%00111110,%00000000,
%00000000,%00011100,%00000000 ]
}
irq {
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ubyte smoothx=0
sub irqhandler() {
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smoothx = (smoothx-1) & 7
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main.perform_scroll = smoothx==7
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c64.SCROLX = (c64.SCROLX & %11111000) | smoothx
}
}