First of all, it's awesome to see a game that has a Linux build! Thank you so much for that.
The game is really fun already. The idea might not be overly original but it is very well executed. It's very satisfying to lead the snake (or basilisk) down a dead-end and then hop into a tunnel. However, I think there are a few small, easy to implement, changes that could make it even better:
- The controls can be really unforgiving. I would recommend adding something similar to coyote-time but for the direction changes.
- The apples are super OP. They make all the levels way too easy. You might want to think about limiting the number of apples to 1 per level, or limiting them in some other way.
- Being able to reset the level without dying would also be nice. Similarly, a way to return to the main menu without completing all the levels.
- Finally, the difficulties of the levels were very up and down. Perhaps you could reorder them so that the difficulty is a steady increase.
Overall a really solid game. Hope my feedback helps! :D