It's a nice game! But I see a few mistakes here and there.
The first that jumped to me is the pew pew sound. The mood of the game is rather grim with sacrifices, blood and bats... and we get a basic pew pew. It felt out of place to me. The music is nice though! Simple but nice.
Second is the respawn after making a sacrifice. I got killed on spawn several times before even getting to see the screen! At first I thought the upgrade killed me. You need to make enemies spawn at a reasonable distance from the player, at least almost a screen. This can even be considered a bug as it prevented me from playing the game.
Third, I don't really know how I did this but at one point after getting an upgrade I got a second instance of the music playing over the first. Make sure you can't call the music several times at the same time in your code :)
Overall I liked the graphics, the animations and the idea a lot but there are a few mistakes in execution. Thank you very much!