bitplane-thingie/bitplane-thingie.p8

pico-8 cartridge // http://www.pico-8.com
version 41
__lua__
-- bitplane-thingie
-- by kistaro
-- mastodon: @kistaro@dragon.style
-- matrix: @kistaro:chromaticdragon.net
--
-- dev tool for experimenting
-- with bitplanes and palettes

function _init()
 cls()
 -- reset bitplanes
 poke(0x5f5e, 0xff)
 -- enable mouse
 poke(0x5f2d, 0x1)
 
 -- reset mouse position
 last_segment = nil
 segment = nil
 was_click = false
 cx, cy = 0, 0
 
 -- reset color
 plane_mask = 0xff
end

function _update60()
 restore_under_cursor()
 if stat(34) & 0x1 == 0 then
  -- mouse up
  was_click = false
  segment = nil
  return
 end

 -- ignore drag off ui
 if was_click and segment == nil then
  return
 end

 -- mouse down
 local mouse_x = stat(32)
 local mouse_y = stat(33)
 
 if mouse_y >= 112 then
  if segment then
   mouse_y = 111
  elseif not was_click then
   handle_ui_click(x, y)
  end
 end
 
 if mouse_y < 112 then
  local r = 1
  if segment then
   local dx = mouse_x - segment[1]
   local dy = mouse_y - segment[2]
   r = sqrt(dx*dx+dy*dy)
  end
  segment = {mouse_x, mouse_y, r}
 end 
 
 was_click = true
end

function _draw()
 draw_ui()
 draw_segment()
 draw_cursor()
end

-->8
-- draw_segment

function draw_segment()
 if (not segment) return
 
 color(0xff)
 poke(0x5f5e, plane_mask)
 circfill(unpack(segment))
end

-->8
-- ui (and click)

function draw_ui()
 poke(0x5f5e, 0xff)
end

function handle_ui_click(x, y)
end
-->8
-- draw_cursor

function draw_cursor()
 cx, cy = stat(32), stat(33)
 
 -- save blob under cursor to
 -- corner of sprite sheet
 -- to restore on next frame
 poke(0x5f54, 0x60)
 poke(0x5f55, 0x00)
 palt(0, false)
 sspr(cx, cy, 8, 8, 120, 24)
 palt(0, true)
 poke(0x5f54, 0x00)
 poke(0x5f55, 0x60)
 spr(stat(34)+1, cx, cy)
end

function restore_under_cursor()
 palt(0, false)
 sspr(120, 24, 8, 8, cx, cy)
 palt(0, true)
end
__gfx__
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