Picopelago commented source code

picopelago.p8

--Created by Eric Billingsley. This code is licensed under the Attribution-NonCommercial-ShareAlike 4.0 International license (CC BY-NC-SA 4.0): https://creativecommons.org/licenses/by-nc-sa/4.0/

--clear screen & sprite sheet
cls()
memset(0,0,0x1000)
--color ramps
--increase elevation
r={2,3,4,5,6,7,8,9,10,11,12,13,14,15,15,1}
--decrease elevation
r2={0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,0}
--height to shadow color
rs={1,1,8,2,9,9,8,8,8,8,9,9,9,9,9,0}
--water sparkle palette
rw={2,2,3,12,[0]=1}
--height to unshadowed color
rpost={1,1,2,3,4,5,6,6,7,7,7,13,10,11,12,0}
--screen palette
pal({1,140,12,135,9,139,3,131,5,134,6,7,13,132,133,129},1)
palt(0)
mode="title"
selection=0
o=0
draw=1
x,y=64,64
sparkles={}
function dirtyline(y)
	dirtylines[mid(127,flr(y))]=true
end
for y=0,255 do
 --sparkles are two pixels in
 --a horizontal line, random
 --distance apart
 x=flr(rnd(128))
	sparkles[y]={x,x+flr(rnd(4)),flr(rnd(4))}
end

--sspr that wraps screen edges
function ssprwrap(x,y,w,h,yoffs)
	for sy=y,y+h-1 do
	 --h was meant to be 1 here but I didn't catch it.
	 --seems to look ok as is and
	 --fixing it increases compressed chars
	 sspr(x,sy%128,w,h,x,(sy+yoffs)%128)
	 sspr(x-128,sy%128,w,h,x-128,(sy+yoffs)%128)
	 dirtyline(sy%128)
	end
end

--refresh screen 
--(mark all lines to be 
--redrawn from height data)
function rf()
	for i=0,127 do
	 dirtyline(i)
	end
end

function _draw()
 --draw to sprite sheet 
 --(where we keep height data)
	poke(0x5f55, 0x00)
	dirtylines={}
	--select mode
	if mode=="title" and btnp(❎) then
	 mode=selection
	 rf()
	 if mode==1 then
	 	cls()
	 	poke(0x5f2d,3)
	 end
	elseif mode==1 then
	 --redraw lines where
	 --mouse cursor was last frame
	 dirtyline(my-1)
	 dirtyline(my)
	 dirtyline(my+1)
	end
	--get mouse coords
	mx,my=stat(32),stat(33)
 if mode==1 then
  --for draw mode,
  --set draw coords to mouse
  x,y=mx,my
 end
	for n=1,16 do
	 --move coords randomly
		x=(x+rnd(4)-2)%128
		y=(y+rnd(2)-1)%128
		--brush size
		draw=mid(draw+rnd"0.5"-0.25,2,mode==1 and 1)
		--only draw if mouse pressed
		--or we're in title/screensaver mode
		if mode!=1 or stat(34)!=0 then
			if draw>1 then
				pal(rnd{r,0})
		  palt(0)
		  --increase elevation and 
		  --move up in y coord for
		  --rectangular area
				ssprwrap(x-2,y,draw*4,draw*2,-1)
				--do it again in a smaller
				--rect if brush size is
				--big enough
				if draw>1.5 then
					ssprwrap(x,y-1,draw*4-4,1,0)
				end
			end
		end
	 pal(0)
	 palt(0)
	 --erosion -- done a bunch of
	 --times on the same line so
	 --fewer lines dirtied
		erody=flr(rnd(128))
		for n=1,20 do
			erodx=rnd(128)
			--erode downwards only for
			--3d effect. vary x offset
			erod2x,erod2y=(erodx+rnd{-1,0,1})%128,(erody+1)%128
			col1,col2=pget(erodx,erody),pget(erod2x,erod2y)
			--randomly add or subtract
			--1 from erosion result
			--for more variation
			toadd=rnd{-1,0,0,1}
			--only erode if difference>=2
			if col1>col2+1 then
			 --bring the 2 points closer
			 --together in height
				pset(erodx,erody,col1-1+toadd)
				dirtyline(erody)
			 pset(erod2x,erod2y,col2+1+toadd)
				dirtyline(erod2y)
			end
			--if we find max height pixel,
			--decrease height of whole map
			--(small probability)
			if col1==15 and rnd()<0.001 then
				pal(r2)
				sspr(0,0,128,128)
				rf()
			end
		end
		--vary which pixels of a
		--sparkle are visible
		sparkles[flr(rnd(255))][3]=flr(rnd(4))
	end
	--draw to screen (final rendered
	--image)
	poke(0x5f55, 0x60)
	--only draw dirty lines
	for y,v in pairs(dirtylines) do
	 --shadow height
	 s=0
	 pal(rpost)
	 --draw whole line with
	 --unshadowed colours
	 sspr(0,y,128,1,0,y)
	 pal(rs)
	 --step through line and
	 --calculate shadows
	 for x=0,127 do
			col=sget(x,y)
			if s>col+0.5 then
			 --in shade, draw shadow color
				pset(x,y,col)
			elseif col<5 and ((sparkles[y][3]>1 and sparkles[y][1]==x) or (sparkles[y][3]%2==1 and sparkles[y][2]==x)) then
				--draw water sparkle 
				--(no sparkles in shadows)
				pal(rw)
				pset(x,y,col)
				pal(rs)
			end
			--update shadow height
			if col>s then
				s=col
			end
			s-=0.5
		end
	end
	pal(0)
	--draw title screen
	if mode==1 then
	 ?"\31",mx-1,my-1,12
	 pset(mx,my,0)
	elseif mode=="title" then
	 pal(0)
	 rectfill(0,29,127,50,2)
	 rectfill(0,83,127,96,2)
	 selection=(selection+tonum(btnp(⬆️))-tonum(btnp(⬇️)))%2
		?"\^t\^wpICO\|hp\|fElAgO",25,32,3
		?"\^t\^wpICO\|hp\|fElAgO",26,31,12
		?"BY ERIC BILLINGSLEY",29,44,12
		?"sCREENSAVER MODE",33,84,12
		?"dRAW MODE",33,91,12
	 ?"❎",22,84+selection*7,1
		?"❎",22,83+selection*7+4*t()%2,12
	end
end