Turret Defense is a wave-based tower defence game. Enemies march along a fixed winding path toward your base, one wave at a time, and your job is to line that path with turrets and destroy everything before it gets through. You start with 20 lives, and every enemy that reaches the end of the path costs you one; run out and the base falls and the run ends there, with your wave count, kill count and score locked in.
Select Gun or Frost from the build bar, then tap any open grey tile along the path to place it — turrets can only be built on valid empty tiles, not on the path itself or on top of another turret. Tapping an existing turret upgrades it instead of placing a new one, up to a maximum of level 3, and each upgrade raises that turret's damage, range and fire rate together rather than just one stat, so an upgraded turret is meaningfully stronger across the board, not just harder-hitting. When your defence looks ready for the next wave, press Send Wave to start it. On desktop, number keys 1 and 2 select the gun and frost turret respectively, and Space sends the next wave without needing to click the button.
Gun turrets cost 40 gold, fire relatively quickly, and deal solid single-target damage — they're the damage backbone of most defences and the turret you'll place the most of. Frost turrets cost 60 gold, deal far less damage per hit, but slow anything they strike to half speed for as long as the slow lasts. A frost turret placed early on the path effectively multiplies the value of every gun turret positioned after it, because enemies spend roughly twice as long inside those turrets' range while slowed, which means twice the shots landed on them before they move on. Neither type stacks in cost as you build more of them — the price shown is always the flat cost of the next one, so there's no penalty for leaning heavily on whichever type your layout calls for.
Every turret automatically fires at the enemy furthest along the path within its range — the one closest to actually breaching — rather than the nearest or the weakest, which is almost always the correct priority since it's the threat with the least time left to deal with. Standard enemies are the baseline, balanced in health and speed. Orange runners start appearing after the first couple of waves and move noticeably faster while carrying less health, so they reward turrets with fast fire rates or wide coverage over raw single-hit damage. Every fifth wave has a chance to bring a red heavy enemy with over three times the health of a standard enemy at reduced speed — heavies are exactly where frost's slow effect earns its keep, since extra time in range compounds against a target that already takes a long time to kill outright.
You begin a run with a starting gold stockpile, and gold from there comes from two sources: a bounty for every enemy killed, which varies by enemy type, and a completion bonus paid out once an entire wave is cleared, which grows larger as the wave number climbs. Because that completion bonus scales with wave number, a lean, efficient opening that doesn't overspend on turrets you don't need yet ends up funding a considerably stronger mid-game than an early run that spends every coin the moment it's earned. Waves don't start automatically — nothing advances until you press Send Wave — so there's no time pressure between waves beyond your own judgement of when your defence is actually ready.
Build at corners. The path in this level design doubles back on itself several times, so a turret placed in the crook of a bend can cover two or three separate lanes of traffic as the same enemy loops past it repeatedly, which is worth far more than placing the identical turret along a single straight stretch it only sees once. Upgrading an existing, well-positioned turret is usually better value than spending the same gold on a brand-new turret in a mediocre spot, since the level-2 and level-3 stat gains apply to a position you've already confirmed is good. And because targeting always favors the enemy furthest along, a strong turret cluster near the start of the path does relatively little work compared to the same cluster placed where enemies are forced to linger longest — so it's worth thinking in terms of total time-in-range across the whole path, not just raw turret count.