Nice and polished little game, had fun playing it.
Some thoughts:
- Early on it always feels better to take risks since you don't have much to lose. It might be interesting if players had to risk not only session gems but also meta gems, might make the dynamic more engaging;
- Later in the game, gems and some upgrades start to feel useless since you don't really need them anymore. Maybe if upgrades had to be purchased each session, gems would stay relevant throughout. Combined with the first point, that could make the risk/reward loop even stronger.
Would love to hear your thoughts. Overall, really good game.