Exploration style platformers (pitfall, indiana jones games, etc.) have never got it quite so right as Spelunky. The game manages to achieve a feeling of real exploration, mostly because the levels are randomly generated.
Each level that you play is entirely unique, owing to the game’s clever level generation algorithms. The levels are destructible, so you can always find your own route through them. The idea of each level is to reach the end whilst collecting as much treasure as you can. There are gems, coins, and even golden skulls; which set off a joyfully predictable rolling boulder which crushes everything in its path.
There are lots of hints toward the Indiana Jones movies; the whip, the hat, and of course the boulder.
The enemies in Spelunky are cute but deadly, and there are a variety of ways to kill them. There are spike and arrow traps, and the placements of enemies and traps often makes the game very difficult.
Whilst the graphics and sounds of Spelunky have a cute feel, they are often at odds with the games feeling of exploration. The best levels are dark, and you’ll need to carry flares to be able to see. Straying too far from the light can mean you end up running into an enemy or falling to your death, and this gives the game a sense of suspense which is often absent from the lighter levels.
The lighter levels have an arcade feel, and really the game is about collecting all the treasure you can. If you enjoy platformers, this is one of the best.
TL:DR: A delightful indie platformer which is different every time you play. Charming graphics combined with endless replayability make this a must play for anyone interested in indie games.