20: Sphinx Hijinks

Campaign

Waves: 9

Starting Energy: 1800

Lives: 20

Three enemy spawn points, one teleporter, and two checkpoints to defend. Unfortunately, there are two bottlenecks you need to look out for. You have to properly divide your forces to defend both of them, especially the one near the teleporter. Concentrate your forces in the roads near the checkpoints. Once you amassed enough energy, build Mini-gun towers and Quad-Beam towers. Also, fully upgrade your infantry towers to vanguards, preferably with EMP grenades. If you see Behemoths or just several enemies grouped together, don't hesitate to rain down missiles from above. As usual, be careful of the usual annoyances like Blinkers. Two squads of infantry (not in combat) can stop them but to avoid any risks, you may further reinforce these positions with additional squads.

With the number of waves and enemy types, you can surely rack up enough energy to fully specialize your towers and even buy their special abilities. You don't have to fill up the entire tower slots. Having powerful towers near your key chokepoints is more important.

Veteran

Waves: 6

Starting Energy: 1400

Lives: 1

Setup your infantry towers to guard the checkpoints then build at least two upgraded laser towers. As the battle drags on, upgrade your infantry to LV2 to be able to hold off most of the current enemy types, then get your two main laser towers to at least LV3. Place additional towers along the winding road as well. Around in the third wave, you'll encounter behemoths that will be joined in by enforcers. Target the enforcers first then focus fire on the behemoths. The final wave will consist of mirages and jolts so at this point, you should already have fully upgraded specialized towers.

Spec Ops

Waves: 1

Starting Energy: 1950

Lives: 1

The initial wave is already unforgiving, with several mirage, orbweavers, and enforcers. Don't hesitate to use a Tesla charge when they're grouped together to get a massive energy boost for the kills. In the later part of the wave, behemoths will appear accompanied by blinkers. The last part of the wave will consist of a massive number of dry grunts and sand slingers so use your tesla charges and airstrikes to kill most of them at once. Make sure you prioritize upgrading your infantry towers and change them to Vanguards to hold off most of the enemies, allowing you to easily target them with a well-placed airstrike.