One of the ideas I had long, long ago was a side scrolling shoot-em-up that would sort of double as a rhythm game (yes, I thought of this while Guitar Hero was still big). The general gameplay idea I had was to either have the enemies appear in time to the music, or have the notes of the melody play when you shoot the enemies, so that doing well would give you more of the song. I might still use this idea at some point, but my first attempt back then to sync enemy appearences to "Don't Fear the Reaper" was a right pain in the arse.
The other idea idea I had for it was that the enemies appearances would all based on musical notation, instruments, and equipment. Stuff like a dragon with a microphone for a head and a spine made of aux jacks, a frog/saxaphone hybrid that belches stuff at you, and attack CD's (although i think i've seen those in a few other shoot-em-up's).
At this point, I'm more concerned with getting a decent work routine set up so that I might update more than once every 6 months, so I wanted to scale back to some simple, arcade-y style projects while we work out the kinks. And so, I kept the idea of making everything music-themed, and started to re-create Space Invaders. Right now, I have a functionally, albeit dirt simple, version running (see below). I do need to make the enemies shoot back, put in some kind of level progression, and some other extras, but it is (technically) playable.
(Jeez, youtube compressed the heck outta this vid)
I'm currently going with making the player ship shaped like a guiter. In this case, just because they're both roughly the same shape.
If we ever get to fleshing this out into a full, gradius style game, I was toying with the idea of making the ship chage shape based on what power-ups it has. Something like speed-ups would make they back grow out into a v-shape or defense-ups would give it a rounder look, like an acoustic guitar. It could be a nice bit of flair that doubles as a visual indicator of player power level.
I wanted the enemies to be based on musical notation and instruments, and I've got some sprites for some basic enemies here:
A bat like monster whose wings and body shape are based on two mirrored eigth notes. It's just a basic monster that goes down after one shot.
Is this a ghost? or more of a wizard? Maybe something else? Eh, I dunno. It's arms are upside-down eighth rests, and the rest just kind of followed from there. Another basic enemy that only needs one shot to kill.
Sort of a "boss monster" akin to the abductor ships in Galaga. Right now, it's only special feature is that it takes two shots to take out. Made from a mirrord pair of upside-down treble clefts.