Great idea ! The dimension shift feel really good and the visual effect is spot on.
The train idea is a fun one and works well with the whole dimension thing, and the shooting is kinda weird looking but feels fun.
Sometimes you can have rocks overlapping each other in two dimensions, and that feels super unfair. Only solution I've found was jumping between wagons, but then you can stay there for the whole game and never be challenged.
I overall liked it, that was fun !