Protips:
1. In general, don't over-buy towers. I beat the last level Brilliant with only 10 towers all maxed out (as level 29).
2. Ghost Crypt > Chilling Crypt. For the last few levels, if you mainly have crypts as the towers in front of where enemies spawn, a max upgraded Ghost Crypt can possibly 'cancel out the enemy's boost effects'. This is extremely efficient against ninjas and other enemies (healers/hasters) later in the game.
3. Don't always be in such a hurry to upgrade your towers. If you upgrade your towers in the front as soon as upgrades are available, chances are the towers in the back toward your gems won't even get EXP. Then when ninjas arrive, your towers in the back are too weak to kill the ninjas before they grab a gem. Make sure you upgrade your towers evenly for the best effect (starting with the ones in the back).
A Mix of fun with a little skill. Funny Inserts and simple and clear gameplay makes this an excellent time killer. The only downside is the restriction, although the game is still very fun within itself.
Excellent Game 5/5!
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