Puzzle Map Idea

OK so i just had a good idea that people might have come up with already but here it is:

So if any one is already planing a puzzle map here is an y idea for them. using a grenade launcher with manual detonation you would need to bank the grenade off of several walls the open a door of some sort to move on to the next stage

this is just an idea if you like you can use it i am not going to make a puzzle map