Each board feeds enemies down two traces that converge on your core, and every wave is divided between them, so no single node can hold the whole map. You choose between covering the junction where they meet — cheaper, but enemies survive most of the way in — and defending each trace separately, which kills them earlier but costs twice as much.

Nodes that are placed next to each other combine. For example, a Damp node adjacent to a Chain node becomes Superconduct, and an Amp node boosts the nodes around it. Position matters as much as which node you build, so plan adjacency before you plan coverage.

Placing a node uses it up, so after each build your hand is empty again. If you picked the wrong one, tap Drop on the strip above the board, press Esc, or right-click the board. Tapping one of your own nodes while holding another also drops it and selects that node instead.

Phasers cannot be targeted by normal means and Flyers ignore the path entirely, going straight over your defences. Both require you to build answers specifically for them rather than relying on raw damage along the route.

Each node can be set to target First, Last, Strongest or Closest enemy. Switching modes to suit the incoming wave — for instance, setting a heavy hitter to Strongest against armoured units — is often more effective than buying an upgrade.

Calling the next wave early with the double-arrow button awards bonus gold, which compounds into a stronger defence later. It is worth doing when your current setup can comfortably handle the overlap, and risky when it cannot.