function _init()
   init_sound()
   init_mapgen()
   init_player({block_size/2, block_size/2})
   generate_map({0, 0})
   debug = false
end


function _update()
   handle_input()
   handle_map_update()
   if (btn(5) and btn(4) and btnp(3)) debug = not debug
end

function _draw()
   rectfill(0, 0, 127, 127, 0)
   -- the screen is 128x128 pixels, so it fits 16x16 sprites
   map(camera_pos[1], camera_pos[2], 0, 0, 16, 16)
   draw_player()
   if debug then
      render_debug_info()
   end
end

-- decide whether we need to regenerate the map.
-- if so, call generate_map appropriately and reset coordinates.
function handle_map_update()
   if out_of_bounds(camera_pos) then -- out_of_bounds() checks all screen bounds
      -- we need to regenerate the map, so we generate a map chunk that
      -- places the player in the middle of it.
      generate_map({player_pos[1]-block_size/2, player_pos[2]-block_size/2})
      camera_pos = {block_size/2 - 8, block_size/2 - 8}
   end
end

function out_of_bounds(pos)
   return pos[1] < 0 or pos[1] > block_size-16 or pos[2] < 0 or pos[2] > block_size-16
end

function render_debug_info()
   clip(0, 0, 32, 24)
   rectfill(0, 0, 32, 24, 0)
   print(stat(0), 0, 0, 15)
   print(camera_pos[1], 0, 8, 15)
   print(camera_pos[2], 16, 8, 15)
   print(player_pos[1], 0, 16, 15)
   print(player_pos[2], 16, 16, 15)
   clip()
end