Thank you so much for your thoughtful and detailed feedback! It's really encouraging to hear that you enjoyed the game, especially given its development in just three days.
I appreciate your suggestions and insights. Regarding the lag issue, there are indeed many crystals spawning and not enough of them clump up which in addition to many enemies spawning and people playing in the WebGL version may lead to worse experience. In current implementation crystals check if they can merge only when they appear, so i think it is optimized correctly. Although I also implemented a system where dark blue crystals should merge into crystals of other colors but it doesn't seem to work in current version :(
The concept of allowing players to pick up every crystal on the map with special red XP orbs is a fantastic idea. Your enemy suggestions, like the bees and frogs, are intriguing and would certainly make the game better.
If I decide to continue developing this game I'll definitely consider implementating your ideas.
Again, thank you for your support and constructive feedback!