Very interesting idea.
The mouse desync (on WebGL at least) makes things a bit hard but not too bad.
I found it a bit weird that the snake had no issues going through it's own body after a deadend, maybe it could reward the player with some bonus points, or maybe even some special blocks? Currently, it seems that a player can just place blocks as fast as they can and try to create a maze asap. What do you think about adding a timer for refreshing the blocks? That would limit the speedrunning-type of gameplay, you could then give out some powerful blocks to player when the snake hits itself to reward the player for strategic planning.