No-Upgrade-Limit Spike Factory

The No-Upgrade-Limit Spike Factory has one path with infinite upgrades. At base, it acts like a normal Spike Factory, with 5 pierce and 1 damage per spike. The range equals a normal Spike Factory

Bigger Stacks ($455)
Stacks of spikes can pop 10 bloons.

White Hot Spikes ($625)
Spikes can now pop lead and frozen bloons.

Larger Steel Spikes ($850)
Spikes pop 20 bloons and 3 layers.