Zooshi

The classic open-source 2D platformer starring Tux the penguin, with lots of levels.

A cross-platform Chinese chess (Xiangqi) game built with Qt, with play against the computer, two-player mode and network play.

An educational 2D platformer that teaches game hacking: use memory editing and assembly tricks to solve levels.

A hardcore action platformer: play a demon trapped in a ball, mixing Souls-like difficulty with unique ball-based platforming. Full source released.

Godot 3.6.1 / ROTA: Bend Gravity / Gravity Bending Block Puzzle Platformer Game

A WebGL 3D platformer made with three.js, playable in the browser.