Tower Defense

Three towers, three jobs

Creeps follow a fixed S-shaped road from the entrance to the exit, and every one that reaches the end costs you lives. You stop them by building on the empty cells beside the path, and the three tower types are meant to work together rather than compete:

• Gun (the circle): fast firing, low damage per shot. Cheap, reliable, and the backbone of any defence against ordinary creeps.
• Cannon (the square): slow but hits with splash damage, so it punishes bunched-up groups. One well-placed cannon can soften a whole cluster at once.
• Frost (the triangle): deals little damage but slows every creep in range, buying your other towers extra seconds of firing time.

New players skip Frost because its damage looks pitiful, and that is the single biggest mistake in the game. A slow kills nothing by itself. What it does is multiply everything else: creeps crawling at reduced speed spend far longer inside your guns' range, which works out the same as adding extra guns for the price of one triangle. Damage clears waves, but slow is what makes the damage land.

Place for the bends

Where you build matters as much as what you build. The turns of the S-path are gold, because creeps spend the longest time in range there. Better still are the cells tucked inside a bend where the road doubles back on itself: a tower there reaches two stretches of path at once and shoots everything twice, once coming and once going. Before you place anything, work out which cells touch the most road.

A setup that carries most games: Frost on the inside of a bend, a Cannon beside it so the splash lands on the slowed clump, and Guns filling the other cells that touch two legs of the road. The creeps bunch up in the cold, the cannon hits the whole bunch, and the guns pick off whatever crawls out the far side.

Money only comes from kills

There is no allowance here. Every coin comes from a dead creep, so an early leak hurts twice: you lose a life and the income at the same time, and a weak start snowballs into a poor defence three waves later. Tap a tower you own to upgrade it, up to two levels. An upgrade is usually a better buy than a fresh weak tower, because it stacks power on a cell you have already proven good. Selling returns seventy percent of what you paid, so every sale burns thirty percent. Treat it as a repair tool: sell between waves to fix a genuinely bad placement or to re-tool for what is coming, never in a mid-wave panic.

Ten waves, then the boss

The waves grow in number and toughness, and the tenth brings a boss that walks straight through a thin defence. Plan for it from about wave seven: bank some money instead of spending every coin, then pour it into upgrades on your bend cluster just before the end. Against one tough target, splash matters less and steady sustained fire matters more, so a fully upgraded Gun or two sitting next to your Frost earns its keep right at the finish. If the boss still gets through, the usual reason is that your slow did not cover enough of the road, and it only met full-speed towers.

One more habit separates clean runs from near misses: watch the first creep of each new wave walk the whole road once. You will see exactly where your coverage goes quiet, and that silent stretch is where the next tower or upgrade belongs. The game hands you this scouting report every wave for free; most players are too busy building to read it.

A quick word on the genre

Tower defence grew out of player-made maps for strategy games in the late 1990s, and it took over browsers in 2007 when Desktop Tower Defense, a simple Flash game by Paul Preece, drew tens of millions of players. Everything that made the genre stick is present here in miniature: a fixed path, towers that trade damage for speed or control, an economy fed by kills, and the constant question of whether to widen your defence or deepen it. Ten waves and three towers strip it down to a tight little exam on the basics: cover the bends, slow the pack, and keep a few coins back for the boss.