At it's core, Spelunky is a precise 2D platformer, with a very simple yet elegant scoring mechanic. Each level through which you descend is littered with treasure, and your objective is to get to the end of the game, beat the boss, and escape with as much gold as you can carry with you. This would get a bit boring if the levels were the same every time, so instead the layout of the platforms, items and enemies changes every time you retry, although the four themed areas (plus one special, secret one) always appear in the same order. Interestingly, in this version, there is a daily challenge: a seed is generated and every one who attempts the daily challenge will play the same seed, and the scores are ranked at the end. Best I've achieved is twelfth in the world. Mind you, the disparity between my score and that of the person in pole position was enormous.
It probably took me a good twenty hours of practice before I could reliably make it to the second set of levels.
You can buy and find a variety of different items to help you proceed but you always start with just four bombs and ropes. Spelunky is a tough game, for sure, and you'll need to put the effort in if you want to see all that it has to offer. Although it is possible for RNG to generously hand you a seed with a few more items and a few less traps, the randomisation isn't so extreme that luck alone is enough to make or break a run. A skilled player will always succeed, no matter what, whilst someone who hasn't quite grasped the mechanics can have all the advantages and still squander them. Death in Spelunky often comes quite quickly, and cautious play is advised. As you practice, you'll learn how to be cautious and plan ahead, whilst still being very speedy and efficient with bombs and ropes. This is important, as levels in Spelunky are timed; when the clock hits 2:30, a ghost will emerge from the nearest wall and if it touches you, your run is over.
It really put me off at first, the idea that I couldn't take my time and explore all the nooks and crannies, hoovering up every tiny speck of gold as I went. But, the ghost is essential in encouraging you to get better, to find the fastest and most efficient ways down through the level, and skilled players can even exploit its appearance for fiscal gain. Like so many aspects of Spelunky, what seems like a hardship at first gradually reveals itself to be a boon. The angry shopkeepers, a real nuisance, but when you learn how to handle them, their shops become a little treasure trove for you to plunder. Could save you a few pennies in the black market, for sure.
They say the devil is in the details, and Spelunky is full of little flourishes which really vitalise the whole experience and imbue everything with character. Take the red frogs, for example. They explode on death (a problem, or a boon?) but if they go into water, even in their death throes, they'll transform into a blue frog. It's really neat discovering stuff like that for yourself, so, sorry for spoiling that one :P
There are loads of secrets too! Most levels have just one way out, but what happens if you try to get the crown from the skeleton in the haunted jungle level, and just what is the deal with that weird, tumorous growth sprouting from the backdrop? Does it have a use? That's up to you to find out, and you'll feel great when you do. Spelunky has produced more moments of elation and awe for me than any other game I've ever played, and I finished Dark Souls.
Listen, you owe it to yourself to play Spelunky. It might be the best game ever made.