Build your arsenal. Bank the Gold your converts drop and spend it on a 14-node upgrade tree between rings:

• Main Gun — multishot, fire rate, raw damage
• Rockets — homing volleys that chain to a second target
• Laser — a steerable charged sweep beam
• Defense Orbs — orbiting bodyguards that intercept and ram
• Hull — more HP, faster orbit
• Turncoat — make your converts hit harder