itch.io

Uses two-dimensional "sprites", 2D images created and used on a flat plane, as opposed to the three-dimensional models or environments found in 3D games.

Things that are available on GitHub

Games using the engine LÖVE, a 2D cross platform game engine where you code games in Lua.

Games that can be played alone

The larger universe outside of Earth's atmosphere. Sometimes really, really far outside of it.

Games where the primary goal is keeping the player character alive under harsh circumstances such as dwindling resources or a hostile environment.