var directions = {
  "right": {
    "degree": 0,
    "dx": 1,
    "dy": 0
  },
  "down": {
    "degree": 90,
    "dx": 0,
    "dy": 1
  },
  "left": {
    "degree": 180,
    "dx": -1,
    "dy": 0
  },
  "up": {
    "degree": 270,
    "dx": 0,
    "dy": -1
  }
}