Very interesting concept! Having to go between the mortal realm and the underworld and keeping both sides ok is very challenging! I think the game can be a little more forgiving, but nonetheless, the game is very well-designed and well-made. The control feels good, and the SFX fits very well.
To make this game better, perhaps it is a good idea to reduce the number of temples in the underworld. I feel like above, there are only 3 temples, but in the underworld, there are so many, and the timer is very short. Instead of increasing the difficulty by having more temples, perhaps you can add other mechanics to add variety to the gameplay.
Overall, a very well-executed fun game. Very impressive that you managed to make everything functional and running by yourself in 10 days! Keep up the good work!