Tidal rhythm reopens channels every 30 seconds; sea-urchin turrets and anemone mines must cover rotating entry points. Kelp shadows hide enemies from long-range towers. Signature: cut kelp with urchin spikes to reveal ambush lanes.
Underwater emerald and jade, swaying kelp forest, god-rays, drifting spores and silt.
Click, Enter or Space to start. Place and upgrade towers with the mouse and number keys, or by tapping on touch, to stop each enemy wave before it reaches your goal. The HUD tracks lives, cash and wave.