Fun 20 minutes! Music is cool, maybe beef up the bosses a bit (then again I play a ton of FPS, some people might not agree).
Just an idea; I would love a time attack mode with a counter in the top corner. With an intro/outro sequence skip button, this is the perfect game to speedrun and grinding out an optimal route would be cool considering the game's mechanic of slowing down hurting your overall time. (With a quick reset button!)
I'm following you now and can't wait to see what you do in the future.
(Oh, and I found a bug where I hit slow-mo as it was empty/about to charge, and it kept me in slow-mo as it filled up indefinitely.)