Let’s talk about Tower Defense

Tower Defense is probably the most recent sub genre to appear in the last few years; a form of strategy game where the primary object is to keep stuff out. There’s a ton of Tower Defense games out there, primarily on the web, but downloadable and mobile, too.

A primer for the initiated:

Gemcraft, on Kongregate
Bloons 3, on Kongregate

Warzone Tower Defense, on Newgrounds

(There’s a great second one on Newgrounds, and likely elsewhere too, that features a number of mission styles, a campaign, and experience levels on both the towers [training] and the castle. If anyone finds it, let me know and I’ll add it to the list here.)

The main element you’ll see in any of these games is a static board wherein enemies enter and move towards a fixed location (generally a base, or the end of a path), often along a fixed path. The player is then tasked with setting up stationary defensive structures — the eponymous Towers — to stop those enemies from reaching their goal. In many cases, the game is endless until failure which is typically caused by a preset number of enemies reaching the goal.

Tower Defense games are exceptionally popular, but a lot of them are very bad. In many, there are clear, single strategies that are superior; the players are often given lots of options, most of which are terrible. Most TD games suffer from a complete lack of balance and planning, making games that are shallow, frustrating, and not all that fun.

This is why I’ve listed the 3 I have. Gemcraft features several unique ideas including a slow scaling of player abilities, and a unique take on producing the towers; it’s re-playable missions encourage players to try new strategies again and again on older scenarios. Bloons is quite traditional as the genre goes, but has several viable strategies and the most E-rated flavor of any of the TD games. Warzone includes open paths, and a few scenario types, which offer a variety of interesting strategies.

So what makes some TD games better than others? Well, variety and balance, ultimately. Since most TD games have shifty balance, and narrow strategy (often because of shifty balance), fixing those elements (by fixing balance or by adding strategy) can vastly improve the genre games.

Bloons and Warzone offer balance in different ways. Bloons has narrow damage ranges for attacks, a small selection of weapons with highly distinct properties. Warzone includes more weapons that are better balanced across cost/usefulness benefits; moreover, it offers the players a lot of strange and interesting choices by making the enemies path-find across an open field, letting the play try to maze them up and expose them to more attacks over time. Gemcraft has poorer balance, but it’s also not controlled — players are randomly given gems and made to deal with them — but counters this lack of control by letting players do more with the gems, such as moving them, combining them and using them as disposable items.

So, that’s cool. What else could we do? Well; like before, we gotta make sure a TD game is balanced, and it really helps to add another avenue of strategy. Now, TD games are innately simple, and generally demand replaying to get good at, so to appeal to the mass, you want to make sure you don’t add too many new/different mechanics to the game — you’ll want to make sure the mechanics you use are both effective and interesting if you want it to work.

So what mechanics? Well, no TD games I know have the enemies assault the towers, either as a temporary halt or permanent damage. This would make the players need to both replace or repair towers over time, and protect towers from attack. What else? Well, Gemcraft lets you move gems around towers, but I don’t know any games that let you actually move towers; that could have a low cost associated with it, or perhaps the player never builds towers, only upgrades and moves.

More? Many TD games include a method to slow down enemies; some allow you to divert by blocking (like Warzone) but none let you do more direct movement modification — maybe a magnet to drag enemies in a particular direction, or treadmills. Or how about giving the player a base with specific components, where losing each component bares a penalty (or maybe components are added with success) so protecting individual components becomes important.

Lots of interesting things we can add in here. TD is fairly flexible. But why?
Well, because strategy is a very broad genre — Tower Defense is simply a limitation of that broader genre; one player builds and defends, the other attacks. This limitation is what leads the sub genre to it’s general imbalances, as it often fails to account for the fact that the sides are asymmetrical. Balancing asymmetrical sides is tricky! We often avoid it for just that reason — but when it works, it can work very well. (Of course, more about asymmetrical game design another time.)


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One Response to “Let’s talk about Tower Defense”

  1. online games Says:

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