Open source gem:
Mari0 (pronounced “mari-zero” or “mari-oh”) is a 2012 side-scrolling platform video game developed by German[1] indie developer Maurice Guégan with creative input from Sašo Smolej and released onto their website Stabyourself.net. It combines gameplay elements from Nintendo’s Super Mario series and Valve’s Portal series. The game features Mario armed with a “portal gun”, the main game mechanic in the Portal series, allowing him to create two inter-spatial portals on 2-dimensional surfaces which can transport himself, enemies and other objects through them. It was made with the LÖVE game framework.