It took me a while to get what I needed to do (clicking left to fire only worked sporadically, holding left to fire was the way to go, why the first level ended), but then it was pretty fun.
Story wise, have I got it right that the guy is taking something illicit to stave of his nightmares for a while, but eventually* the nightmares come for him after all.
*I noticed the patern in the pill-section of the level looped, and didn't seem to get much harder after one loop, in which case you could actually keep it up perpetually.
I'm not entirely clear how the Mandalas work. I saw nearby nightmares dying occasionally, but I couldn't figure out what determined if it worked or not. Is it a damage-over-time effect while they are nearby or something? There isn't really any feedback. I see there's a little yellow light around them, so maybe you could have that light flare up when it's doing its thing, or something like that.
And one minor point, there seems to be an occasional glitch that shows a black line below the pill sprite, which appears and vanishes as I moved forward:
