I'm working on a Sonic fangame that doesn't star Sonic. My idea is an exploration-based game. Essentially, you start with 2 jumps (you can jump at any time you have a jump left on your meter. walking off a cliff doesn't take away a jump, so you could get some rings below a platform and then double-jump back up onto the platform). There's a Chaos Emerald that grants you another jump. Lives and the time over are gone. Lava puts your rings at zero but can't kill you (explained ingame). There's another Chaos Emerald that gives you the Flame Shield's ability. I'm thinking of going somewhat Metroid-style rather than level-style.
My problem is this: I can't exactly approach level design from the standard Sonic angle. I don't want to make it play like Metroid, either. As far as exploring, yeah, but I want it to feel like a Sonic game. Does anyone have any design tips?