Lara Croft's co-op Aztec platformer is free, so long as you don't mind ads.
Lara Croft and the Guardian of Light, the clever platform puzzler from 2010, has been revived as a free to play browser title. So long as you don't mind the occasional advertisement, you too can help Lara and the deathless guardian Totec defeat demonic Xolotl. On the other hand, if you're willing to spend $9.99, you can have the experience ad-free.
The folks over at Core Online snagged Square Enix's platformer. It's not immediately clear how well Guardian of Light, which integrated co-op so well, will perform as a browser-based game. Though playable as a solo effort, the game's co-op function was a big part of the fun; it'd be a shame if the browser version didn't allow for that.
Lara Croft and the Guardian of Light has Lara seeking the Mirror of Smoke, only to discover that it comes complete with an ancient curse of world-shattering potential. She and her newfound ally Totec have to put Xolotl back in his box before dawn, or everything ends.
Source: Game Informer