Lara Croft and the Guardian of Light is now a free-to-play browser based game. The game is being released using Google's Native Client on Chrome. It is currently available for both PC and MAC users. The down side is the free version of the Lara Croft and the Guardian of Light has ads. If you wish to play without ads, you can pay $9.99 for the full version of the game.
There are 10 missions available, and each can be accessed at anytime.
If you're at work, or school, it would probably be wise to spend some time checking this game out in your browser. I recommend typing a lot every now and then before sighing and hitting the backspace a few times. No one will suspect you're actually knee deep in a Toxic Swamp!
Note: If you're playing on a MAC you have to use Chrome.