Algodoo

When the scne starts, the box still has collision 1(A) and this makes it able to collide with the little box which also has collision group A. Simply set the collision group of the box at the beginning to B and it should work

Also move the lasers a bit inside the frame. else, the laser get's blocked before the box even hits the beam. Best you set the frames collision group To 4(C), and the lasers script to e.geom.collideset = 1 to = 5 and e.geom.collideseet = 2 to = 6. Then you pretend that the box falls out of the frame