A weird solve challenge that I've contemplated a few times but never really tried, and I don't think I've posted about. It's a sort of visual bandaging.
Pick a colour, and hold the cube so that 3 faces are visible. Only turns which keep all stickers of the chosen colour visible are allowed (including slice moves). That is, the only legal states have all stickers of the chosen colour on 3 adjacent faces (meeting around a corner). Make sure to scramble like this too, I have no idea if any state with stickers on 3 adjacent faces can be reached from the scrambled state, though I suspect it wouldn't actually be a problem. Also, turn carefully as it would be easy to accidentally break the rule.
I guess a strategy would be to try to get all the stickers back onto one face (might be difficult), then work out algs which preserve that.
I'd be impressed if anyone could manage this.
Edit: don't know if I got lucky or not, solved a layer.