I just started on my game, Crisis of the Chrononaut.  Here's a repeat of the game summary:

You're an apprentice to a genius inventor. Suddenly, the time machine he's working on goes beserk, then disappears. It seems the machine he was building is now tearing apart the fabric of time. Portals start appearing that connect to other times, including Cretaceous Period, Medieval times, and WWII. You can enter the different eras and explore, but hostiles from each of these periods can emerge to fight you as well. Your mission: enter the portals, find the missing time machine, and destroy it before shatters time itself.