Vent Line

A tower defense where every turret overheats, and you score by venting each one at the moment its heat ring hits the green arc.

Date: 2026-11-05 Genre: Tower defense Platform: Mobile (portrait, touch-first) Status: Playable build

Concept

Blobs crawl a zigzag path toward your base, and ten pads sit beside it for turrets. The turrets fire on their own, but each shot adds heat. Left alone they jam, so the real job is deciding which tower to vent next and when.

How to play

Tap an empty pad to spend coins on a tower. Tap a built tower to vent it. If its ring is in the green arc (70% to 95% heat), the vent fires a burst that ignores armor and puts the tower in overdrive for 3 seconds. Venting early or late wastes the heat and locks the tower for 0.9 seconds. Letting it hit 100% locks it for 2.5 seconds. Ten leaks end the run. On desktop, click pads, or press 1-9 and 0; R restarts, P pauses.

Core mechanics

• Towers auto-fire at the enemy furthest along the path. Each shot adds 12% heat, and heat bleeds off slowly.
• A vent in the green arc deals 7+ damage in radius, ignores armor, and doubles fire rate for 3 seconds with no heat gain.
• Consecutive green vents build a combo multiplier up to x5. A bad vent, an overheat, or a leak resets it.
• Towers level up every 10 kills (to level 5) for stronger bolts. Build cost rises 15 coins per tower owned.
• Purple tanks take only 35% damage from normal bolts, so green-vent bursts are the answer to them.

Progression & scoring

A wave arrives every 22 seconds, or 4 seconds after the field clears. Wave 1 is grunts only. Runners (speed 98) join at wave 3, armored tanks (16 HP, cost 3 hearts) at wave 5, and swarms of tiny fast blobs on odd waves from wave 7. Grunt and runner HP grow 10% per wave and spawn gaps shrink to 0.5 seconds. Score is each kill's points times the current combo multiplier, so a long clean streak is worth far more than steady safe play. Best score is saved locally.

Look & feel

Dark slate board, mint green for the safe zone, amber for coins and the base, purple for armor. Everything is drawn on canvas inside a portrait phone frame, with a screen shake and a short hit-stop on a perfect vent. Sound is WebAudio beeps and sweeps, unlocked on the first tap.

What makes it fun

• Every tower is a small timing test running at once, and the greedy play is waiting for 94% heat when the overheat is a single shot away.
• Spending coins on a new tower competes with the safer habit of venting the ones you have, and a new tower starts at 0% heat, so you have to wait out its first climb.
• Tanks force you to stop relying on bolts and aim bursts at the right tower as they pass its range.
• When you lose, you can name the cause: a late vent, an overheat, or a tank that got through.