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.

Godot Engine - The free and open source 2D and 3D game engine

Pretty sure everything is indie on itch.io but just in case you want something extra indie.

Games that can be played using only a mouse or other pointing device, and don't require any other input.