I really appreciate the interactive tutorial which explains how to play in detail. I only missed the win/loss conditions and how to gain or lose hearts. The option to replay without the long intro would also be nice.
I think the minimalistic design fits the game very well. But I would prefer a different control scheme: using Q,E, X, arrow keys and a mouse is not convenient for me. I think WASD instead of arrows could work fine, or switching between views with a mouse.
Overall, it's an interesting idea and well executed, despite a couple small issues. Great job!