The Gameshelf

Since I've been playing and thinking about tower-defense games recently, it occurred to me that it might be interesting to have a reverse tower-defense game, where you plan out the hordes of monsters that get shot at by towers. Thinking that this was unlikely to have been a completely original thought, I searched around and found Anti-TD, a game that came out two years ago.

(It's part of the Anti Games Series by Sugar-Free Games. It also includes Anti-Match3 (I guess this could be fun if you were a fan of the genre, but it's not my thing. Although it does apparently have a two-player mode, where one person plays the dropper and one person plays the matcher, which is interesting) and Anti-Pacman (you play all four ghosts. When you're not controlling a ghost, it wanders about on its own. When you are controlling a ghost, you move it around with the arrow keys. When a ghost dies, it is gone for good, so you don't have it available for later levels. Jason, you should at least check it out for the art that it shows you between the levels. While researching this, I also ran into the game Pac-Man Vs. for GBA and GameCube, where one person plays Pac-Man and up to four others play the ghosts. They get around the inherent unfairness by letting Pac-Man see the whole board (on the GBA) but letting the ghosts only see the area around themselves (on the TV screen). When a ghost gets Pac-Man, the two players switch places).

Anti-TD is not a very good game beyond the concept. For one thing, it took me about 30 seconds to discover a winning strategy that made the game too simple to care about. Let me explain. You are presented with a board that has paths and towers on it. You can select a type of creature and an entrance, and then send it. Your goal is to get a certain number of creatures to the exit alive. There are about a dozen different creatures, and they come in five different levels each (each one slightly faster or more resistant than the last). The only stats the creatures have, however, are unit type (ground or air), speed, and resistance. In each of the 10 levels, you start with a certain amount of money. I very quickly noticed that when I sent some creatures out, even though they died, I ended up with more money than I started with. I guess you get some money just for having your creatures spend time out there or something. So I picked a fast unit and then just kept sending those out, and my money built and built. Eventually, either that unit would overwhelm the defenses or I could save up enough money to buy a bunch of the top unit and push those through. I won the game in about half an hour.

Besides being absurdly easy, there also isn't much opportunity for strategy in the game. There are different tower types, but you can't click on them to find out anything about them, and there's certainly no indication that different units are affected differently by the different types of towers. And as for picking a path, it's simply a matter of counting the number of towers on each path and picking the one with the least defense. There are also little power-ups that appear and disappear randomly, but they really don't add much to the gameplay.

So, what should a good reverse tower-defense game have? Here are some initial thoughts.

• It should allow you to see what the towers are. Maybe it doesn't give you the full stats, or at least not until you've had a few units gunned down by that type of tower, but you should at least be able to tell what it does by clicking on it or hovering over it.
• It should have different creature types have different strengths and weaknesses in relation to the different tower types. This can be done in any of the ways any of the various tower-defense games have done it: associate creatures with different elements, have them walking or flying, give them resistances or susceptibilities to different tower types, etc.
• It should have some logical (or at least explained) way that you get resources. Maybe you get resources over time. Maybe you get resources for destroying towers or for getting creatures to the end of the board.
• It should have some kind of upgrade mechanism. In Anti-TD, all of the creature types are available to you from the beginning as long as you can afford them, and you can afford most of them in the first level. Part of the fun of a tower-defense game is being able to upgrade your abilities or at least upgrade the towers. It should work similarly for upgrading monsters.

Asymmetric multiplayer tower defense might also be an interesting challenge to design. In regular tower-defense games, your goal is to slaughter wave after wave of your enemy. In a reverse tower-defense game, your goal would be to overwhelm the defenses. How would this work with one player playing the monsters and one player playing the defender? It would be a challenge to make the game fun for both people, since it's unlikely to be much fun to get all of your guys constantly slaughtered. Also, if there is any kind of planning between stages, the timing would have to be such that it doesn't take one person 10 seconds and another 3 minutes to decide what to do next (I guess a timer could easily solve that). It might be interesting to play a series of matches, where each player gets experience and is upgrading and such as the matches go on, but where the players have totally different roles. Are there games out there like this?