Dark Castle was one of the first games I played on a Mac, way back when they were black and white. The game was a clever platform jumper/puzzle solver that had you coming back for more. You explored a Castle and fought a Black Knight at the end; in between you threw rocks at robots, birds, etc., maced a torturer, and avoided the bad guys while getting to the exit of the particular level.
I had always wanted to play the game again, and a company called Super Happy Fun Fun (yes really) not only redid the original game – in color to boot – they also added many levels in the tradition of the original. This game is Mac only, but you can check out a demo, buy the game, and get more info at the Return To Dark Castle web page. Check it out for some old style, 2D gaming fun.