Thank you for your nice comment! I agree, it is tough to find the treasures, there should at least be coins to lead you to them.
If you'd like to discover the rest of the world, here are the four treasures' location:
- On the antenna of the first telescope at the right of when you begin the game
- Atop the altar on the sky temple
- In front of the ancient lighthouse at the right of the tower
- At the top of the tower
This will then unlock a purple portal which the rings next to the top of the tower lead to, in the second dimension, activate the rings until your friend screams something about corruption, inside the central orb another portal awaits you.
Thank you for playing!!