Spelunky is a pure arcade cave platformer, where you go as deep as you can through randomly-generated dungeons. That's really about it. There's no overarching story, no over-the-top CG, no real main character. Just you, your whip, and your wits. And, before you know it, you died.
The main learning mechanic here is not the "jumping-on-enemies-like-Mario" attack, nor is it the platement of bombs and ropes to better nagivate the dungeon. Nope, the main learning mechanic is...CRAP I DIED AGAIN!!
(Starts again) You see, most platformers simply mark your death as a "whoops, you fell in a pit" or "you let the enemy touch you in your no-no zone," give you a "life lost" screen wipe, and send you again on your merry way. Not Spelunky. They make your death clear as a journal entry, with a full "last words" phrase commenting on your death. The picture is not even a picture, but a still-filming camera showing your body slowly dying. When you fall on spikes, watching your character slowly sink into the spikes really hits home. I remember...FUCK WHERE DID THAT ARROW COME FROM???
(Starts again) Okay, I have to remember those rocks with faces shoot darts. But when do they shoot? Oh, that bat ate it bad with an arrow. THAT'S IT!! (throws rock in path...*dink*!) There you go! No more arrow! Much of the game is this, just learning from your mistakes, especially the ones that make you dead. Hey, a golden idol, just like those in Indiana Jones, where you grab it *grabs* and some giant boulder comes rolling do- wait, what's that rumbling? OH MY GOD!!!! WHERE DID THAT BOULDER COME FROM?????
(Starts again) You'd think that this constant dying would turn someone off from Spelunky, but then you'd be dismissive of their audience. They're looking for players who don't mind the constant maiming, who want to push their luck and see how far they can go. I reluctantly want to say they're attracting the "casual" gamer, because there's nothing casual about this game. Every choice you make is tense, even the simplWHAT THE FUCK??? THAT'S LIKE A 50-FOOT DROP!!!
(Starts again) Throughout the game, you'll also come across items to help prolong your journey, and damsels to save. For example, you can pick up a jetpack along the way, making reaching to or descending from high places safer. You can get paste that'll make your bombs sticky. You can even find an ancient artifact that can help you locate hidden treasure. There's even the random merchant who will sell you goods, relieving you from your well-earned gold. Of course, if you're brave enough, you can blow up the shop from below and steal the items from right below the merchant's RUUUUUUUN!!!! HE HAS A SHOTGUN!!!!!
(Starts again) Yeah, blowing up the merchant's store results in him coming after you with a shotgun, screaming "terrorist." If you don't like dying a lot, you won't like this game. The learning curve is extremely steep, and there will be times when you will just have a run of extremely bad luck. Once, I fell down a pit that was a smidgen too high, so I got knocked out for a moment and lost one health, no big deal. The moment my character stood up, however, I took an arrow to the face, which propelled me back into another pit and into a bed of spikes. Worst. Day. Ever.
But when you do get further, there's so much more the game will show you, so even progressing to the next level is a self-reward in itself. And, with everything being randomly generated, the gameplay is never the same game. Sure, you know how to avoid danger anywhere, but will you know how to if they're laid out in a specific pattern? I once saw a ladder with a section on either side: one side had the damsel, the other had an arrow-loaded statue. No thanks.
So, if you're up for a quick challenge and don't mind having to restart over and over again, Spelunky's the game for you. Just don't outstay your welcome, or els- AAAAAAHHHH!!!! A GHOST!!!!!