Ok, this was seriously good! And it's starting with the title- "Gastronoir"! Sounds equally disgusting and intriguing!
Let's go through the things! The graphics were great. From the intro you know you are in for a treat. The gameplay animations were great too. If I were to nitpick, I'd say that maybe that floor could have more texture? Or the guy could have a more visible attack animation? That's nitpicking though! Because you know what's the real winner? how the game gives you feedback. After killing the first heart, and seeing the animation I instantly knew what my objective was, no text exposition needed! Also- the screen shake was a nice touch!
Lat's move on to the sound. After killing the first heart I knew what I had to do, but at that time I also knew the level was kinda large. Not a problem, though, because I was lead by the heartbeat! I loved this! Most of the jammers struggle with audio, some opting for sparse sound use and some background music (me included). Hewr, you had sound give you navigation hints! Loved it!
The gameplay? The difficulty increased at a nice pace. After I died on fourth heart, I was afraid I'd have to play all of the previous ones again, but no! Checkpoint system works great in conjunction with the difficulty, because the last heart made me die a lot :) One problem I had was with the lack of the fullscreen option in the web build. In the heat of the battle I often moved my mouse out of play area, and that caused me to stop shooting, and that broke my flow a bit.
The usage of the theme was ok. There was something missing here. Like I didn't feel that "one room" affected the gameplay.
Over all- great gameplay, great animations, awesome sound design! Keep it up man!