Was a bit glitchy and confusing for me, but it seems to be a decent core to work from for making a stealth game as most of the mechanics worked fairly well. Some of the mechanics were a bit confusing:
*Tutorial was pretty lacking: not apparent at all that walking into someone would kill them. Buttons were all over the place as well: why is it two different buttons to enter and leave a grate instead of the same button?
*Some doors seemed like they could only be opened by guards, so you need to follow them in. Cool, but this wasn't immediately apparent, and you can get yourself stuck in an unwinnable situation if you kill all the guards without realizing it. It'd be helpful if guards kept respawning so you don't get stuck, or if the game tells you you're stuck and resets.
*If you walk into a view cone it freezes you as it slowly fills up with red, but the view cone is already so short I don't know why the red part even exists (though I suppose it provides a bit of forgiveness, which is nice, but the view cones are already incredibly tiny).
*The sound circles worked very oddly for me. They weren't stopped by walls (this is ok, but maybe this could be changed), and they deployed way after the guard died or the whistle blew instead of immediately, creating a weird disconnect. Also, sometimes the circle could grow slowly, and other times it would just pop-up: weird graphical glitch.
*Sound is kinda lacking at the moment: gets annoying to constantly hear the negative errnt sound of guards seeing blood or odor or whatever.
*Unlocking abilities with exp I feel is something that shouldn't be in as it makes the design very weird, but if you do keep it in, it'd be helpful to see how much something costs before spending exp.
Looking forward to seeing where it goes from here!