Thanks so much for playing and for spending so much time with the demo!
About the yellow gems — I set the drop rate too low. That’s my mistake, sorry about that.
For reference, in Level 5 they’re more likely to drop from the charging bats and the plant-type enemies that surround you.
The drop rate also increases the further you progress into the level.
Thanks again for the feedback, and I’m really glad you’re looking forward to the full game!
I appreciate the honest feedback on the music as well — I’ll take that into consideration for future updates.