I have pictures for all 40 waves. After 30 it gets a little tricky and I had to try a few times before I got it. But basically since this game’s towers have no special effects like slow, its all about damage and rate of damage, so in the early going (Levels 1-30), its just better to get basic towers and then sell them for better ones when you can until you reach wizard towers.

Starting setup:

Just a simple setup with two sentry towers in the center of turn circles to cover the most room. The key to the early levels is just to upgrade the damage on towers. Specifically look at the enemy HP for each level if the damage of your two towers can equal or be greater than the enemy’s HP, your doing well. Don’t be afraid to sell if you can afford the next high tower. The damage of the next level tower is usually better than upgrading. If your damage does not add up to be greater than the enemies’ HP and you can’t afford the next higher tower even after selling, then upgrade your damage until the sum of the damage of your towers can match a single creep’s HP.

Level 10:

You can see I have a Crystal and an elf tower by this point and upgraded as needed.

Level 20:

Two wizards by this point. For this, I upgraded both wizard towers to full since they are at the pivot point where they can do the most damage. Upgrade damage, speed, and range for these two towers only.

Level 30:

Yep, still the two towers upgraded pretty much to max.

Level 40:

You can see I have several wizard towers upgraded all to max damage and all except one upgraded to full range. All are at max fire speed. I have two sentry towers as “attack absorbers” because they are cheap HP towers and can be repaired at the rate of 3G for each 10 HP. I have them in those positions because then the enemies will attack them first instead of my wizard towers.