scambier · July 22, 2022 15:16
diff --git a/bouncing.lua b/bouncing.lua
 --[[
 The idea of this tweetcart was to get the "water ripple" effect with a grid of points.

 Each point is applied a sinusoidal effect,
 	depending on its distance from the center, and the elapsed time.

 The points go up then down following that sinusoidal,
 	and a color gradient is applied to get a nice pseudo-3d effect.

 You can copy-paste this whole code inside PICO-8 and just run it.
 Play with the values to see what changes!
 ]]

 -- Smooth framerate!
 _set_fps(60)

 -- Blue gradient palette.
 -- This command overwrites the default palette, but leaves black as index 0.
 pal({7,12,-4,-3,-11,-15,1},1)

 -- Set camera position to -64,-64
 -- so the origin 0,0 is at the center of the screen
 camera(-64,-64)

 -- Start of loop
 -- This is a goto ::<label>::, where <label> in this case is just an underscore
 ::_::

 -- Clear screen
 cls()

 i=0
 for y=-44,54,4 do
 	-- The i counter, with "+(i%4)" here,
 	-- is used to place points in an alternating pattern.
 	-- Definitely not necessary, but looks better.
 	i+=2
 	for x=-64+(i%4),64,4 do

 		-- a and b are the vertical and horizontal distance between the point and origin,
 		-- normalized to the range 0-1.
 		-- a is divided by 80 (instead of 64) to give a more rounded shape
 		a=x/80
 		b=y/64
 		-- Pythagoras, c²=a²+b²
 		-- We don't sqrt() here, because we don't need the exact distance - saves chars and processing time!
 		dist=a*a+b*b

 		-- z is the vertical offset that we apply to each point.
 		-- The basic idea is to (at least) call sin() with the elapsed time t() and the distance.
 		-- This way, all points at the same distance from the center will get the same offset,
 		-- forming concentric circles.
 		-- From there, we play with the values to get the desired effect.
 		z = cos(-sin(t()*.15 - dist/6)) * 10

 		-- Draw the point
 		pset(
 			-- The horizontal position of a point never changes.
 			x,

 			-- The z*1.2 is to smooth some light ripples between the big waves.
 			y + z*1.2,

 			-- The color is also calculated from this offset.
 			-- Since z varies (roughly) between -9 and 9, (z+10)/18 normalizes it to 0-1.
 			-- This value is then *6+1 to get a color index between 1 and 7, corresponding to the palette.
 			((z+10)/18)*6+1
 		)
 	end
 end

 -- Draw the screen
 flip()

 -- Back at the start of the loop
 goto _
	--[[
	The idea of this tweetcart was to get the "water ripple" effect with a grid of points.

	Each point is applied a sinusoidal effect,
	depending on its distance from the center, and the elapsed time.

	The points go up then down following that sinusoidal,
	and a color gradient is applied to get a nice pseudo-3d effect.

	You can copy-paste this whole code inside PICO-8 and just run it.
	Play with the values to see what changes!
	]]

	-- Smooth framerate!
	_set_fps(60)

	-- Blue gradient palette.
	-- This command overwrites the default palette, but leaves black as index 0.
	pal({7,12,-4,-3,-11,-15,1},1)

	-- Set camera position to -64,-64
	-- so the origin 0,0 is at the center of the screen
	camera(-64,-64)

	-- Start of loop
	-- This is a goto ::<label>::, where <label> in this case is just an underscore
	::_::

	-- Clear screen
	cls()

	i=0
	for y=-44,54,4 do
	-- The i counter, with "+(i%4)" here,
	-- is used to place points in an alternating pattern.
	-- Definitely not necessary, but looks better.
	i+=2
	for x=-64+(i%4),64,4 do

	-- a and b are the vertical and horizontal distance between the point and origin,
	-- normalized to the range 0-1.
	-- a is divided by 80 (instead of 64) to give a more rounded shape
	a=x/80
	b=y/64
	-- Pythagoras, c²=a²+b²
	-- We don't sqrt() here, because we don't need the exact distance - saves chars and processing time!
	dist=aa+bb

	-- z is the vertical offset that we apply to each point.
	-- The basic idea is to (at least) call sin() with the elapsed time t() and the distance.
	-- This way, all points at the same distance from the center will get the same offset,
	-- forming concentric circles.
	-- From there, we play with the values to get the desired effect.
	z = cos(-sin(t().15 - dist/6)) 10

	-- Draw the point
	pset(
	-- The horizontal position of a point never changes.
	x,

	-- The z*1.2 is to smooth some light ripples between the big waves.
	y + z*1.2,

	-- The color is also calculated from this offset.
	-- Since z varies (roughly) between -9 and 9, (z+10)/18 normalizes it to 0-1.
	-- This value is then *6+1 to get a color index between 1 and 7, corresponding to the palette.
	((z+10)/18)*6+1
	)
	end
	end

	-- Draw the screen
	flip()

	-- Back at the start of the loop
	goto _
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