Thanks! I spent a large portion of my time trying to get the raycasting to work well (except the bug where the game randomly crashes, which may or may not be caused by the code for it). I didn't know about The Lost Vikings; all I knew about was Fireboy and Watergirl, which must have been heavily inspired by it.
Strange that the sounds didn't work... I suspect it's due to my mistake of first saving the new settings and then changing the volume in the game, so if the saving throws an unexpected exception, it can't get to the part where it changes the volume. I didn't experience that issue myself while testing the browser version, but it may vary from browser to browser and machine to machine. Regardless of whether this is the issue, I'll swap those lines of code just in case.
The reason I have the sound off by default is so that I don't accidentally burst the player's eardrums. I think this should be a standard everywhere, not just in games but also in embedded videos, music/SFX websites, etc. However, I should definitely set the SFX and music volume to at least 50% by default while the master volume is at 0% so that the player doesn't have to adjust all 3 sliders.
I should have probably added some optional hints for level 10 4. It would have taken much less time than my original plan of making more levels.