Upgrade or build? The question every wave asks

Every tower defence run comes down to a stream of small money decisions, and the biggest one is whether to upgrade what you have or add something new.

Early on, breadth usually wins. More towers means more coverage, and coverage keeps you alive through the first chaotic waves.

Later, depth takes over. A fully upgraded tower at a key chokepoint often out-damages three cheap ones, and it doesn't clutter your map.

My habit is to build until my chokepoints are covered, then pour everything into upgrades. Switching too late means you're spread thin against tough enemies.

Watch your income carefully. If you're ending waves with lots of leftover money, you upgraded too cautiously. If you keep barely surviving, you built too wide. The sweet spot is spending almost everything, every single wave.