code: func (f *Field) IsBlocked(x, y int) bool {
  	if x < 0 || fieldBlockNumX <= x {
  		return true
  	}
  	if y < 0 {
  		return false
  	}
  	if fieldBlockNumY <= y {
  		return true
  	}
  	return f.blocks[x][y] != BlockTypeNone
  }
docs: // IsBlocked returns a boolean value indicating whether
  // there is a block at position (x, y) on the field.