case Input.dir4
when 2
move_down
when 4
move_left
when 6
move_right
when 8
move_up
end
改为如下内容：
case Input.dir8
when 2
move_down
when 4
move_left
when 6
move_right
when 8
move_up
when 1
move_lower_left
when 3
move_lower_right
when 7
move_upper_left
when 9
move_upper_right
end