Play Dr. Mario Nes Online

Remember Dr. Mario? This NES classic is basically Tetris with a medical twist. You're dropping these two-colored pills into a bottle full of nasty viruses. Match three pill halves (or combo with viruses) of the same color—red, blue, or yellow—and they disappear. Sounds simple, but those viruses multiply fast. First time I played, I kept stacking pills too high and panicking when they neared the top.

There's a chill single-player mode, a frantic time trial, and my favorite: two-player battles where you can sabotage each other by sending extra garbage pills when you clear lines. The music's weirdly catchy too—that little victory jingle when you clear a level still gets stuck in my head.