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.

Games where you have to manage resources in order to complete objectives. 

Involving mathematics

Games which have short playtimes and can usually be completed in one sitting.

Focused on using its text, moreso than its visuals or audio, to tell the bulk of its story/plot. (Still can have great audio and visuals, though!)

Resources for building and relating to User Interfaces, how the user interacts with your program