This game is not nearly as fun as it could be because of a few confusing and annoying traits.
1. Why can't I choose my own towers? I can't form a defense when I cannot choose my weapons.
2. What's with the removal of the useless rock? If it's useless, to force me to remove it is an annoyance.
3. Why can't I upgrade my towers? I know I can combine them, but I don't want to combine, I want to upgrade.
4. The system is complex. If it's Topaz, put in a Topaz colored icon instead of the lightning bolt with dots icon. If it's diamond, use a diamond icon instead of a snowflake. Skip these other icons as they're confusing.
5. I get 3 new towers per level, but if I hit the space bar and call a next level before placing my new towers, I lose them. That sux.
6. More money, please.