Digfender

Since the cost of each tower type increases as you build more of them, and since each tower level adds more than the one before, quality of towers often trumps quantity. A cluster of high-level towers with range and damage boosts, overlooking a winding path, will be able to mow down hordes of enemies, while a scattering of low-level towers all along the path will do little more than scratch damage to tougher monsters like Yetis.

An ideal start looks something like this:

R I

X D X

---------

where --- is the path, D is a damage support tower, R is a range support tower, I is an ice bolt tower, and X is your choice of fire, lightning, or earth. If you don't have enough resources to build all of them, then start with the two regular towers, then the damage support tower, then the ice bolt, then the range support.

(If you haven't unlocked all of those towers yet, that's okay; you're on a low enough level that you can probably win easily anyway. Range support can take the place of damage support on early levels.)

By configuring your initial towers in a cluster like this, you get two potent attackers, and enemies will be slowed. The ice bolt tower can afford to be further back, as it has long range. It is often both possible and desirable to rely solely on a single cluster like this until all the towers have upgraded to advanced versions.

Once they're getting close to maxing out, you can start building a second cluster further along the path. If you're really wealthy and have plenty of space, an even better setup looks like this:

R X ------

I D X ---

B X R ---

where B is just a blank wall. With this setup, you have 4 towers, all with both range and damage support.

Choosing Tower Upgrades

Each tower has two possible upgrade paths. One is a straight upgrade to the basic tower, doing the same thing except further and faster and stronger. The other is more specialised.

Frost Bolt vs Longshot

Frost Bolt towers are the direct upgrade to an Ice tower, and are excellent in a supporting role, with their enhanced slowing effect. Longshot towers have slightly more range, however, and their individually powerful shots are better able to punch through heavy armour. Furthermore, since freezing effects do not stack, there is less benefit in hitting an already slowed enemy, making the slower rate of fire less of an issue. Both types are quite viable, but either way, space them out well, so that two of them don't usually choose the same target.

Stinger vs Fire Bomb

The Stinger is the direct upgrade to a Fire tower, and has the higher overall direct DPS. However, the Fire Bomb essentially makes an area attack, so if there are many enemies clustered together, it can potentially affect much more. It is easily distracted by fast enemies like bats charging ahead of the crowd, however, so Stinger is generally a more reliable choice.

Branching vs Shock

Branching towers are the direct upgrade to lightning towers, and with 4 simultaneous shots and a slightly higher rate of fire, they have higher theoretical DPS against large groups. However, they suffer when faced with strong individual enemies like yetis. Shock towers are frequently the better choice, as their special secondary ability makes them more versatile, able to either attack 3 separate enemies or focus most of their damage on one powerful enemy. Shock towers are also better able to cope with strong enemies that use weaker mobs as cover, since their secondary attack will unerringly target the strongest enemy instead of the first one. 4 well placed shock towers with ice support can mow down an entire column of yetis, even with distractions like bats.

Splash vs Concussion

Splash towers are the direct upgrade of Earth towers. With a large damage area, they are excellent for hitting groups, synergising well with heavy ice support like a Frost Bolt tower (which can cluster several strong monsters together). They are also helpful when weaker mobs sneak ahead of stronger ones and draw fire, since the stronger one will still be hit if it's not far away.

Concussion towers, however, are more potent when facing strong individuals without mobs concealing them. As well as having more direct damage, their stun ability allows them to entirely stop a powerful enemy in its tracks. With enough concussion towers working together, it is theoretically possible to stun-lock an enemy, re-stunning it faster than it can recover, until it goes down. They also have slightly more range. With enough other towers taking care of the weaker mobs, concussion towers can fill a niche.