Sawmill upgrade is very buggy, it caused all my wood to disappear when buying any wood upgrade and go into negatives during gameplay. Eventually the wood spiralled out of control in the other direction and it spawned so many sawmills that the game crashed with a browser error.
Sacrifice also acted weirdly as it let me sacrifice again immediately for the same amount of points, allowing me to get unlimited prestige points. The number in the UI also doesn't go down when buying upgrades with them(?) so it wasn't clear how many I had.
The game seems fun but the weird behaviour (web version) kind of broke it. :(