Rouge Like

Basic Rouge-like, very user friendly. Point and click. No classes, but character gains specialization by what they choose to use and what armor they pick up. Can be multi-player.

Keep things simple, all hits count for "one", armor stops certain types of hits, not reduces damage. Like Hoplite (or Chrono Trigger) game is very geometric.

Not sure if I want a grid or not. If not a grid, probably click to move, with fairly slow movement (make players focus on strategy rather than timing).

This could also be turned into a space game. Warp gate to warp gate, slow ship progress

Shadows

Monsters can only spawn in shadows. Most monsters, by themselves are harmless, but groups become dangerous - archers protect meat-shields, healers so forth. Your group has to balance fighting the monsters with placing torches. There's also a balance of how spread out to be. More spread out means more light, but less support.

Flares provide a lot of illumination for a short time and can be thrown. Torches must be placed, but don't burn out.

Players have no class, but armor add skills. As do weapons.

Abstract

Inspired by this. Everything is abstract shapes, good for graphic complexity. You can carry a limited number of abilities. Your score only counts if you finish, but then you can start again. You can gather points and power-ups, but each level gets more difficult the longer you are there.