GeoDefense Swarm Strategy
Hard Level 3 - The Race is On.
Ok this level is tough! I tried a bunch of different strategies before hitting on the winning solution. Just getting past Wave 1 is tricky.
I finally settled on the formation shown in the attached photo. You can clear the 1st two waves using just this. I then added one of the top 3 laser towers. This will allow you to get past wave 4 which is the next tough spot. Add the remaining two laser towers in this formation and then start replacing the blasters with lasers. Replace the ones which line up with the creeps path first. Upgrade as you go. Wave 10 is tough to get past as is 14 and 15 but following this strategy should get you there. I'm not sure how sensitive this solution is to build order.
I have seen another strategy using juggling but I try to avoid those if possible. No juggling is required for this approach.
The game hints at using an upgraded blaster strategy but I couldn't get that to work. I would be interested in a solution using blasters - let me know if you managed this.