In my case, i only keep my attention in games with a direct competition whit other gamers. I think it is the clue but i also love all kind of games.

I have not a rounded design for a game but i have one special (i think idea. Last months i have been looking for an idea that turns out to an easy design and a more complicated coded 2D scenary/player movement. ie: When the player collides with the ground, it vibrates, player math based animations and things like that.

I found Bezier curves maths and i think it fits perfect with my idea. The player can move into the curve and the curve can change dinamically. I have tested (push F2 to toggle 2D/3D mode) it with collision bitmaps and modifing a simple collision model for the physics engine and it looks funny. This way you can modify the escenary moving simple reference points in 2D or 3D mode. I want enphasize that this idea comes from a dynamic scenary search and it can fit with your puzzle or side scrolled game idea like a visual core based trick.

In other way, looking for a coded solutions for a 2D player instead of animated sprites, i made a complicated doll with many panels and windows for player orientation changes animations. I drawed it with a basic line mode and a full colored kiddy style thinking in an easy design. This way we can transfer design efforts to coding efforts but sincerelly i prefer 3D games.

Just some ideas, sorry for my english
Salud!

pd. i'll be maindfull for this proyect!