Crush the Castle is the iPhone adaptation of a popular Flash game, a physics-based, medieval-themed artillery shooter with clever levels and quite a few extras.
You control a trebuchet--a powerful and accurate catapult--which you use to topple nearly a hundred different castles, one by one. Aiming takes practice, but the interface is easy: you tap once to set the trebuchet in motion, then again to release your payload. You can also tap to switch ammo, as you earn new types of projectiles such as clusters of stones and even bombs. Your goal on each level is to kill everyone in the castle (from kings and guards to ladies-in-waiting) using the least number of shots, and medals to reward your accuracy.
You have to keep adjusting your aim based on the structure of each castle: different materials (like wood, masonry, and metal) react differently to your shots, but with practice you can often find a way to bring down an entire fortress with just one or two well-placed projectiles. You progress across a campaign map, and you can unlock a second map once you've gotten a medal for every castle on the first map. You can also unlock a free-form castle editor once you've cleared the first map.
A lot of care went into Crush the Castle, and it shows in the game's detailed art and often hilarious audio (with realistic nature sounds providing the perfect counterpoint to the castle residents' resigned groans and collar-tugging yelps). About the only thing missing from Crush the Castle is an easy way to zoom out and judge your trajectory, but otherwise it's a fun download with plenty of replay value for the price.