You move around with the [arrow] keys, and interact with things by hitting the [space] bar when a question mark appears over the protagonist's head. Most of the gameplay is simply accomplished by exploring... easier said than done considering how dark it is. As you search the caverns, you'll come across runes that will not only help you open various doors and activate various... things, for lack of a better word to avoid spoilers. Most doors will only open once you've gathered a certain number of runes, so you'll have to keep your eyes peeled for their tell-tale gleam in the shadows... as well as any other things that may be looking back at you.
While green crystals give off their own glow, blue crystals only light up when you get close enough to them. Why is this important? Because light is the only thing that keeps the creatures lurking in the dark at bay. Because you can't defend yourself, you really don't want to get caught in the shadows, so it's important to learn how to take advantage of light sources... and crystals aren't the only ones you'll come across in the game. You can't manually save the game, but if you close the game window and come back to it later, you can choose to continue from the starting point of the last room you entered. Ditto if anything... unfortunate... were to happen to you.
Analysis: Rune Hunter is a little slow. I don't mean slow as in the protagonist is slow moving, although there's that, too. But the whole thing takes so long to build any sort of momentum that players looking for instant gratification may dismiss it after five minutes. Which would be a shame, because Rune Hunt manages to inject a lot of atmosphere and mystery into its tiny pixel package that makes for a lot of rewarding exploration. There's a sinking sense of dread the deeper you go that you wouldn't expect to find in a game that looks like it was plucked straight out of the NES-era. The game makes great use of light and sound to give itself some wonderful ambiance.
There are a few plot points that require you to be somewhere else for them to happen, but because the game doesn't really tell you to just bugger off and explore, you might wind up hanging around certain areas tapping your foot and wondering why nothing is happening. You might end up wishing for a bit more variation, however, the longer you play. The game can go from "Ooooh" to "RRRRRR!" due to the lack of any sort of map (even one the protagonist could make himself) if you get lost or don't know where to go next, especially when the story moves so slowly. Likewise, once the moving light sources are introduced, the puzzles require a bit more patience, a bit more action, and can be a little frustrating.
Still, Rune Hunt is a creepy, fun, clever take on the puzzle genre. While it does have its issues, and I wished for a more present story, I enjoyed it a lot, and look forward to more from the mind behind it. So throw on your adventure boots, because we're about to go exploring in the deepest, darkest, most monster infested-est pit of the earth we can find. Come on; what's the worst that could happen?