Game design is all about decisions and every one of them affects the final experience. Some of them are bigger and more noticeable but others don't seem to have any impact at first glance.
Lately I have been playing both Sanctum 2 and Orcs Must Die! 2. They both belong to the Tower Defense genre and have a similar set of features.
I'm going to give a quick review of the genre itself to make sure we are on the same page.
In Tower Defense games you are faced with several waves of enemies that will try to destroy your headquarters and to fight them you have at your disposal one or more weapons and some defensive structures. Each wave has a predefined number of enemies and if you manage to defeat all the waves without having you core destroyed, you win.
I want to point out some design differences that led me to be more invested in Orcs Must Die! 2 compared to Sanctum 2. So more so, that I ended up buying a DLC pack for Orcs Must Die! 2 just to play more while getting bored of Sanctum 2 pretty quickly.
These decisions might seem to small or insignificant to change anything but they really influence the way the player experiences the game.
In Sanctum 2 you can only place structures on the ground inside selected areas. The differentiation between them comes in what type of enemy are they strongest against.
In Orcs Must Die! 2 you can place them in the ground, walls and ceilings while not having area restrictions (expect the obvious physical ones). To add to that, you can also place defensive units that will attack enemies on sight and don't occupy any significant physical space. Both wall and ceiling defenses have an action range. This creates a very interesting dynamic, since you have to take into account the entire environment to maximize the potential damage done to the enemies (i.e You need to place the archers on high places for them to have a good sight and to prevent the enemies reaching them). The defenses are also varied, ranging from simple spikes on the ground to trampolines that will make the enemies fly. Comparing to Orcs Must Die! 2, Sanctum 2 just feels too one-dimensional and generally linear in the way the player is able to manage its defenses.
In Sanctum there is always time between rounds to manage your defenses.
In Orcs Must Die 2! You only get 2/3 full-time stops between rounds during a level. Normally you only have 15 seconds to rest. This makes the game more interesting since you have to think faster about what defenses are needed and what doors must be protected next. Those times when you have a full-time stop are a good resting point that allow you to rethink your long-term strategy. Since you can sell already positioned structures and units at the same price you bought them, experimentation is encouraged and you never feel like heading into a dead end.
In Sanctum 2 you don't earn any kind of meta-game currency, and even if you did it would be useless because you can't permanently evolve your character in any way. Any new weapons or towers that you eventually get are unlocked in a predefined order through leveling-up and most of them are just plain better than the ones that came before.
In Orcs Must Die! 2 you earn skulls depending on your performance that can be spent buying new weapons, towers and trinkets. There is no obvious increment in raw power or utility on the new items that become available. You just have more options to choose from. On top of that you can also upgrade an item you already have, and the upgrades themselves are very interesting. You have a normal upgrade that just improves the weapon. This normal upgrade has 3 levels. You also have two other "unique" upgrades that add some kind of special behavior to your item, but you can only have one of them at any time.
This evolution really makes a difference because you become more connected to your character and you begin to try different item combinations and upgrades. And since the better you perform in a level, the more skulls you get and the more items and upgrades you can buy, the player is encouraged to try to find a way to reach the maximum score in each level to buy more and in turn try even more combinations and possibilities.
As you can see, these decisions don't seem to be anything special at first but can have deep effects after playing some hours.
Do you feel the same way? Do you disagree? Do you know any other two similar games where you can detect such design differences? I would love to get your feedback, feel free to reach me through twitter.