Finally, an initial idea.

 

You play a spider (either a jumping one, or a weaving one) – in each level you need to get to the fly. The thing is that everything will be from the spider perspective, so the world rotates such that the spider is always facing UP on screen, but gravity is always in the same absolute direction. You will be able to jump/send web upwards (relative to the spider) – and you need to think of how to do that to get to the fly. Things may kill you on the way, not sure what, exactly.

Hope it’ll work out, here’s an inital sketch:

See you later!

Daniel