Move with the [arrow] keys, and tap [Z] or the [space] bar to swing your itty-bitty sword. As you move about, pay attention to thought bubbles that appear over the hero's head that will give you a clue as to what you need in certain spots. The princess hangs in a cage suspended from the ceiling, and it looks like it should be easy enough to get to her, but the castle keeps changing as you play. Just be careful of traps and monsters; slain enemies can drop gems and healing food, but too many hits and you'll be forced to restart from your last checkpoint.
Technically, Tiny Castle is a fairly straight-forward platformer set up on a Donkey Kong-esque playing field. What's unique about it is the way the castle and its guardians change the further you get; walls collapse, areas flood, monsters change shape, and more. While none of the changes are really tremendous, and unfortunately some backtracking is involved, the whole thing is a very clever little romp that shows how you can wring a whole lot of adventure out of the smallest of environments. It's never really that challenging, but it's delightful to see the way new additions to the area present different obstacles.
In fact, my biggest gripe with the game, aside from how short your sword's reach is, is how painfully slowly the knight actually walks. Okay, suits of armor are heavy, but he's not wading through molasses. It becomes especially annoying whenever you're knocked back down to the bottom of the screen and have to slowly make your way back to the top. He doesn't have to be Speedy Gonzales (he doesn't have the right face for a sombrero anyway), but just fifteen percent faster movement would have made a world of difference.
Although not perfect, and definitely not very long, Tiny Castle is a charming little adventure for the sword-swinging knight in all of us. Although, he's so small you could probably pack like twelve of him in you if you stacked them on top of one another.