expanded_grow_tweetjam.lua

-- clear the screen
cls()

-- make a shorter alias far pico8's
-- "get random number" function.
-- usage: r(10) means "random number in [0,10)"
r=rnd

-- print "grow" to the screen,
-- a weird shorthand for print("grow")
?"grow"

-- draw a green underline
--  (x1,y1, x2,y2, colorIndex)
line(0, 5,  15,5,  11)
-- (pico8 just gives you 16 colors,
-- and you have to pick from those)

-- copy the text from the screen
-- buffer to the spritesheet
memcpy(0,24576,384)
-- (0 is the memory address of the
-- spritesheet, 24576 is the address
-- of the screen buffer, 384 is a length)

-- clear the screen again
cls()

-- draw a zoomed-in version
-- of our original drawing
-- (now in the spritesheet)
-- back onto the screen
-- (https:--pico-8.fandom.com/wiki/Sspr)
sspr(0,0,15,6,11,70,105,35)

-- define a goto-label
::_::

-- pick random x/y position
x=r(128)
y=r(64)+64

-- pick nearby potential
-- grow-to position
u=x+r(2)-1
v=y-1

-- set neighbor-count to 0
c=0

-- iterate through a 3x3 block
-- of pixels around our new spot
for a=u-1,u+1 do
	for b=v-1,v+1 do
		-- check current screen-pixel,
		-- color 0 and color 6 are
		-- the background and grey
		-- (plant-pixels are 3 or 11)
		if pget(a,b)%6>0 then
			-- found a green neighbor
			c+=1
		end
	end
end

-- now we check if our grow-to
-- target is valid...

-- is our start pixel a color-index that
-- isn't 0 or 6?
-- 0 is black, 6 is grey - must start
-- growing from a green pixel!
if pget(x,y)%6>0 then

	-- is the new pixel grey (text)?
	-- if not, can we get lucky with a
	-- 1/10 dice-roll?
  	-- ("plants mostly grow on text")
	if pget(u,v)==6 or r()<.1 then
	 
	 -- do we have fewer than 6
	 -- green-neighbors in our
	 -- 3x3 neighborhood?
	 if c<6 then
	 
	 	-- we're good to grow!
	 	-- draw a green pixel at our
    	-- grow-target position.
	 	-- (color 3 or color 11)
	 	pset(u,v,3+c%2*8)
	 end
	end
end

-- jump back to the goto-label
goto _

-- normally, goto is a bad idea,
-- but it's fewer chars than
-- "while" or "for" in lua,
-- lololol