code: func (p *Piece) isBlocked(i, j int, angle Angle) bool {
  	size := len(p.blocks)
  	i2, j2 := i, j
  	switch angle {
  	case Angle0:
  	case Angle90:
  		i2 = j
  		j2 = size - 1 - i
  	case Angle180:
  		i2 = size - 1 - i
  		j2 = size - 1 - j
  	case Angle270:
  		i2 = size - 1 - j
  		j2 = i
  	}
  	return p.blocks[i2][j2]
  }
docs: // isBlocked returns a boolean value indicating whether
  // there is a block at the position (x, y) of the piece with the given angle.