Tower Defense Basics: Placement, Upgrades and Common Mistakes

The basic loop: plan, fight, adjust

A tower defense level is a cycle. You prepare your defense, a wave arrives, you see how the plan held up, and you adjust before the next one. Whether you are placing towers, heroes or plants, the loop is the same.

In Siege Break, that structure is explicit. A round only starts when you press Fight. Until then you can study the open slots and the heroes on offer, refresh the selection if nothing fits, and decide what goes where. The quiet before each wave is your chance to rearrange. Treat that pause as your main tool.

Siege Break Place your heroes around the fortress and hold the line, wave after wave. Play Siege Break

Placement: start from where the enemies walk

Before you place anything, find out where the enemies come from and which way they go. A defender that is far from the path does nothing. One at a corner where the path turns can reach enemies for much longer.

Siege Break's own advice is to hold the path, so think about which open slots sit closest to it. In Avenger Guard, the point is stated even more simply: a well-placed hero blocks the enemy advance while a badly placed one watches it go by. Put your defenders where the enemies will be, not where there happens to be free space.

Avenger Guard Merge heroes, fortify the battlefield and take back a homeland that was destroyed. Play Avenger Guard

Upgrade or add another defender?

Every tower defense player faces this question. You have resources, and you can spend them on a new defender or make an existing one stronger. Neither is always right.

As a rough guide, add defenders early to cover more of the path, and upgrade once the path is covered. A single powerful unit with nothing around it can be overwhelmed, while a wide line of weak units can be too thin to stop a tough enemy. Avenger Guard recommends upgrading defenses as well as heroes, since a stronger line buys time for your damage dealers to work.

Watch what your last wave did. If enemies reached your base through one side, a new defender there is worth more than an upgrade on the other side. If every wave is breaking through at the same moment, as if the defense is too thin, a stronger unit may do better than another weak one.

Merge-style defense: stronger, not just more

A growing number of defense games add merging. Combine two matching units and you get one stronger unit. In Plant Merge: Zombie War, merging is the whole strategy: your garden army grows in power rather than only in numbers.

The usual advice for these games is to merge whenever you can make a pair and to build strength before you need it. A merge made early helps more than one made in a panic, once the wave is already at the gate. Dark Myth: Monkey Merge adds long-term growth on top, with Gold and Merit Points spent on weapons, talents and buildings. If a stage beats you there, upgrading before you go back in is usually the sensible move. Our article on merge games goes deeper into this genre.

Plant Merge: Zombie War Merge plants into stronger plants and hold your garden against the zombie horde. Play Plant Merge: Zombie War

When defenders double as the mechanic

Some games combine tower defense with a different idea. Pinball vs Zombie has pinballs bouncing around the field, and every time a ball hits a plant, that plant fires. Your plants are both your weapons and your bumpers.

That changes the placement advice. Clustering plants close together lets one ball hit several of them in a row and produces far more shots than a lone plant would. Still, spread your early plants across the grid so there is no gap a zombie can slip through, and spend your sunlight as it comes, because unspent sunlight is defense you do not have.

Pinball vs Zombie Plant your defenses, let the pinballs fly and keep the zombies off the lawn. Play Pinball vs Zombie

Common mistakes

These are the errors that lose the most waves. Each one is a way of reacting to the wave you are in instead of preparing for the next one, so use the quiet time between waves to look at the whole map, not just the spot that is on fire.

• Putting everything in one spot. A single strong cluster leaves the rest of the route undefended.
• Saving resources for later. Unspent resources do nothing, and the next wave is always the real threat.
• Ignoring where you leaked. If something got through last wave, find which side let it through before you add anything new.
• Using special abilities too early. Keep them for the toughest enemies in a wave, not the first one that appears.
• Relying on one kind of defender. A mixed defense handles surprises better than a single type.

Where to go next

Defense games sit in a few categories on the site. The strategy category is the best place to start, and the action category has more of the fast, fight-heavy kind. If you want something with a calmer pace, see our list of the best free puzzle games.