local RGB_PLAYER = 0
local RGB_PLAYER_TGT = 1
local RGB_CRATE = 2
local RGB_CRATE_SOLV = 3
local RGB_TARGET = 4
local RGB_WALL = 5
local RGB_GRASS = 6

RGB_PLAYER = 0
RGB_PLAYER_TGT = 1
RGB_CRATE = 2
RGB_CRATE_SOLV = 3
RGB_TARGET = 4
RGB_WALL = 5
RGB_GRASS = 6
RGB_VACANT = 7

player = nil  -- {x=,y=} coordinate of player in current level

      if cell == RGB_PLAYER or cell == RGB_PLAYER_TGT then
        player = {x=c, y=r}
      end

  elseif chord == 'left' then
    move_left()
  elseif chord == 'right' then
    move_right()
  elseif chord == 'up' then
    move_up()
  elseif chord == 'down' then
    move_down()

  end
end
function move_down()
  if player.y >= #level_state then return end
  local src = level_state[player.y][player.x]
  local dest = level_state[player.y+1][player.x]
  if dest == RGB_WALL then return end
  if dest == RGB_CRATE or dest == RGB_CRATE_SOLV then
    if player.y >= #level_state-1 then return end
    local dest2 = level_state[player.y+2][player.x]
    if dest2 ~= RGB_VACANT and dest2 ~= RGB_TARGET then return end
    move_crate_to(player.y+2, player.x)
    remove_crate_from(player.y+1, player.x)
  end
  move_player_to(player.y+1, player.x)
  remove_player_from(player.y, player.x)
end
function move_up()
  if player.y <= 1 then return end
  local src = level_state[player.y][player.x]
  local dest = level_state[player.y-1][player.x]
  if dest == RGB_WALL then return end
  if dest == RGB_CRATE or dest == RGB_CRATE_SOLV then
    if player.y <= 2 then return end
    local dest2 = level_state[player.y-2][player.x]
    if dest2 ~= RGB_VACANT and dest2 ~= RGB_TARGET then return end
    move_crate_to(player.y-2, player.x)
    remove_crate_from(player.y-1, player.x)
  end
  move_player_to(player.y-1, player.x)
  remove_player_from(player.y, player.x)
end
function move_left()
  if player.x <= 1 then return end
  local src = level_state[player.y][player.x]
  local dest = level_state[player.y][player.x-1]
  if dest == RGB_WALL then return end
  if dest == RGB_CRATE or dest == RGB_CRATE_SOLV then
    if player.x <= 2 then return end
    local dest2 = level_state[player.y][player.x-2]
    if dest2 ~= RGB_VACANT and dest2 ~= RGB_TARGET then return end
    move_crate_to(player.y, player.x-2)
    remove_crate_from(player.y, player.x-1)
  end
  move_player_to(player.y, player.x-1)
  remove_player_from(player.y, player.x)
end
function move_right()
  if player.x >= #level_state[1] then return end
  local src = level_state[player.y][player.x]
  local dest = level_state[player.y][player.x+1]
  if dest == RGB_WALL then return end
  if dest == RGB_CRATE or dest == RGB_CRATE_SOLV then
    if player.x >= #level_state[1]-1 then return end
    local dest2 = level_state[player.y][player.x+2]
    if dest2 ~= RGB_VACANT and dest2 ~= RGB_TARGET then return end
    move_crate_to(player.y, player.x+2)
    remove_crate_from(player.y, player.x+1)
  end
  move_player_to(player.y, player.x+1)
  remove_player_from(player.y, player.x)
end
function move_player_to(y, x)
  local old = level_state[y][x]
  if old == RGB_VACANT then
    level_state[y][x] = RGB_PLAYER
  elseif old == RGB_TARGET then
    level_state[y][x] = RGB_PLAYER_TGT
  else
    error('cannot move player to '..old)

function remove_player_from(y, x)
  local src = level_state[y][x]
  if src == RGB_PLAYER then
    level_state[y][x] = RGB_VACANT
  elseif src == RGB_PLAYER_TGT then
    level_state[y][x] = RGB_TARGET
  end
end
function move_crate_to(y, x)
  local old = level_state[y][x]
  if old == RGB_VACANT then
    level_state[y][x] = RGB_CRATE
  elseif old == RGB_TARGET then
    level_state[y][x] = RGB_CRATE_SOLV
  else
    error('cannot move crate to '..old)
  end
end
function remove_crate_from(y, x)
  local src = level_state[y][x]
  if src == RGB_CRATE then
    level_state[y][x] = RGB_VACANT
  elseif src == RGB_CRATE_SOLV then
    level_state[y][x] = RGB_TARGET
  end
end