@kris Spoiler: My enemy is my friend The first time i solved it, I'd gotten to the point where my yellow bot was safe. So i set about getting rid of as many red bots as possible -- including squishing the ones on the tower. In the end, one remained there, and he was able to walk across to the target! So my enemy (that red bot) was my friend (he walked across the target). Since then, though, i haven't been able to get any red bot to do the same, and have had to solve it the way you designed (probably), sending my yellow bot down the long stairs and up next to the tower.