For those who haven't heard, Defense of the Ancients (or DotA) is a custom map for Warcraft III.
If you have heard this, you may not know that this custom map is played nearly as often as Warcraft III is.
If you have heard this, you may not know that DotA is so balanced and competitive that it has become an official game at the World Cyber Games.
If you have heard this, you may not know that professional companies are attempting to use a similar formula to create a DotA-like game they can sell for profit.
Heard of Demigod, League of Legends, or Heroes of Newerth? All inspired by DotA.
This game is so popular and has caught on so effectively for many reasons, but I think it comes down to balance, simplicity, and replayability.
In Warcraft III players did typical RTS tasks, from gathering resources to building a base camp. DotA gives players only a hero, and the game becomes, for most purposes, an RPG. 5 players square off on each side, with nearly 40 heroes to choose from, each with four nearly-unique abilities. There are three "lanes" per side, divided in half by a large river. The objective is to push through any lane to get to each side's final tower, and destroy it.
For me, this is characterized by variability. The game offers an endless amount of combinations, while always starting in the same way. I'm reminded of chess, with more complexity. Each game involves different heroes, uses of skills, item purchases, and the matchups of heroes in each lane. The goal of the game is simple, but there are multiple ways to push towards the final tower and this is what really fosters the sense of replayability. I've been playing for five years now and haven't seen the same game twice.
This is a game that has infinite combinations, but like any lasting sports game, the core rules are very simple. It's what a player, or coach, or team chooses to do that makes the game extremely complex. A hero only has four skills, and a maximum level progression to 25. One of the four skills is an "ultimate" that typically has a longer cooldown but does more damage/chaos/anything than a normal skill. Each hero may also carry a maximum of 6 items to give various bonuses. There are only three lanes, and some woods, that make up the map. Push to the other team's tower, destroy it, and win. The end.
The heroes are divided into strength, intelligence, and agility heroes. Roughly stated, intelligence heroes are the best initially, with powerful damaging spells, agility heroes are the most fragile but offer some of the most potential for late in the game, and strength heroes are a decent hybrid, with additional survivability but also late game advantages. Heroes can be ranged or melee, chasers, support, stunners, damagers, tanks, summoners, crowd controllers, AoE, snipers, and it's all balanced. There are millions of hero and item combinations, going across 10 different players on a single map, and the game manages (for the most part) to keep balanced. Every hero has a downside. Every hero has a counter hero, or counter item. Each item has a cost, with better ones costing more, that require a stockpile to build up. If you die, you lose part of that stockpile. Risk/reward for better items.
This reminds me too much of chess. It establishes an early game, a mid-game, and a late game. It has pawns (AI controlled "creeps" that give money on death and encourages players to stay in lanes to defend against the creep push, and gain gold from killing creeps) and pieces that are useful early, and some that gain their power late in the game. It has a piece that can't move, but on destruction that's the end of the game, and it doesn't matter how well you did otherwise. Every game starts the same, with players at their home bases, and then with each decision a thousand different games are spawned. There is attacking, defense, and counterattacking. It flows as much as any competitive sport or game, and it does it in such a highly polished and well established way that it makes it easy to come back to.
I really think that DotA is a fantastically effective game due to these above traits, and its what is keeping this game afloat and spawning so many other copies, some (Heroes of Newerth) is very nearly a direct clone with enhanced graphics.
The only real problem this game has is its extremely steep learning curve. If you are new to this game, you will be destroyed over and over and over again. Then you will start to figure out why you died, and then you will die over and over and over again. Only when you learn which items to buy, and what every hero can do to you, and what you can do to them, do you have any sort of chance. And then you will still die for a while, but you may start getting some kills while you're at it.
But if you can get past this, you're looking at a very detailed, complex and balanced game that is consistently challenging and entertaining. I've played a whole lot of games over the past five years, but I'll always come back to DotA for a few sessions, and I don't see myself stopping any time soon.
Curious? Heroes of Newerth is a near-perfect DotA clone, lifting the same balanced heroes and items from the original Warcraft III version. Right now it's in open beta, so grab a key and hop on.