Answer in the Forge. Every right answer pays crystals: harder questions pay more and streaks add a bonus. 123 to answer.
2
Build on the pads. Tap a glowing pad next to the road to build a Cannon, Frost Spire, Prism Laser or Mortar. Tap a tower to upgrade or sell it.
3
Hold the line. Doubts march to your Brain Core. Each one that gets through costs lives. Call the next wave early with Space for bonus crystals.
4
Charge the Meteor. Five right answers charge a Meteor. Press M or the meteor button, then tap the map to strike.
5
Forge helpers. Right answers fill the spark meter; every full meter forges a helper card: Sentry Drones, road Barricades, Frost Totems, Tesla Coils, Nova Charges and Mender Drones. Tap a card (ZXCV), then tap the map to drop it.