My first instinct was to blam this, but I really like the concept. I do however Have some suggestions.
1.You should add some sort of direction indicator. This is a game, and a flash game none the less. I don't know if pressing the left key slowly rotates the character or if each press turns him 90 degrees.
2. You shouladd some sort of indicator of motion. I don't know if pressing the forward and back keys moves me at a constant rate or if it just moves me one step forward. Does the back key even do anything? I don't know.
3. The music/ambien sound seems to die off on its own (without movement, i.e. I just start the game and do nothing and the music goes away) and I wasn't able to discern any difference in the volume no matter which direction I attempted to go. Though as per points 1 and 2 I really had no idea what direction I was traveling in nor how far I had traveled.
Though I am aware that disorientation is part of the draw of the game a person even in a pitch black cave would be able to gain some sort of bearings regarding distance and direction. Also they would be able to tell if they hit a wall (which you also have no indicator of). And those components are seriously lacking in this game. I do think this game has extreemly cool potential to be a wonderfully imersive non-visual type of gameplay. What I would suggest:
1. Add indicators for direction, movement, and when the character touches something.
2. Adjust the sound so there is some difference if you have traveled a few paces. What would be preferable would be to have stereo sound so that rotating the character would give you a different perspective (or some perspective at all as to where the sound comes from).
3. What would probably be the funnest would be to ditch the music all together link in the mic and add an echo type method for determining where to go or maybe keep the music/ambient and use echo rather than physical wall location (which you have to admit would be kind of cool).
Again I love the idea, that gives you 4 stars, I just really didn't love the excecution. I do understand that this is your first flash and I am kind of hoping that either someone will help you out with it or run with the idea because I think it would be a very unique and cool experience if it was done well. so Kudos on that.