reply to ”Does someone tell me how to make the Yochicken move with the first rainbow“ , You may watch this scenerio to find any idea: http://www.greenfoot.org/scenarios/5740

well done! There is another platform game you could refer to: http://www.greenfoot.org/scenarios/4851

Why not use the vector form of the shot line with scalar and direction , then give a slight increment of scalar (say 0.1) in each loop to check if collided with the wall ? I think this would be more precise to forbid the bullet running through the wall.

I'm not very clear how to decide which face of the wall the sight line hits ，in other words ，when to use the decimal part of x coordinate and when to use y's