Gun and Inferno Towers
03/17/2010 by Michael Austin
The gun tower was used as a baseline for all other towers in Defense Grid. Each upgrade of each tower was balanced around the level 1 gun, based on its overall utility across all situations.
Level 1 gun tower - Total Cost: 100 DPS: 10 Range: 3.50 squares
Level 2 gun tower - Total Cost: 300 DPS: 30 Range: 3.75 squares
Level 3 gun tower - Total Cost: 700 DPS: 70 Range: 4.00 squares
Originally, upgrades were 1:3:9 with the red towers being three times as powerful as amber towers, but it became too expensive to do the final upgrade (you had to wait around too long for the money), so we lowered it to 1:3:7. The first upgrade is twice the cost of the base tower, and the second is twice that cost.
It was interesting- originally I thought that upgrades needed to be more powerful since you had to save up the money to place them, but in actual playtesting this was offset by the fact that you could make extra use of a prime spot (one near a temporal tower, or one that was placed near a junction). In many tower defense games, upgrading is an easy decision- several waves in it becomes 'place-upgrade-upgrade, place-upgrade-upgrade', and it was important to us to try and find a balance where the upgrade decisions were actually meaningful and had tradeoffs.
The gun tower can shoot any alien within range, and is the best general purpose tower. Because it's so cheap and easy to put down, it's efficiency at level 1 is a little bit below average; however, by the 2nd upgrade the extra range brings it on par with the other towers. It is a front row gun- any tower in front of it limits the damage it can do, and so it should generally be placed as close to the path as possible.
The inferno tower shoots a wide cone of napalm, roasting all the aliens within. It is balanced with the gun tower if it hits between 2-3 enemies on average while it is firing, and is much more powerful when there are more, and less useful when there are less.
The inferno tower is the first tower that does partial heat damage (which means it heats up enemies so they continue to take damage over time. This does have the side effect of reporting half of the damage it does under 'laser level 1' in your stats, but trust me, it's the inferno doing it!) This makes it more effective against fast enemies (who continue to take damage after they pass through), but less effective against shields (which make an alien immune to heat while they are up).
Here are the basic stats:
Level 1 inferno tower - Total Cost: 150 - DPS: 8.5 - Range: 2.50 squares - Cone: 70 degrees
Level 2 inferno tower - Total Cost: 450 - DPS: 23 - Range: 2.50 squares - Cone: 80 degrees
Level 3 inferno tower - Total Cost: 1050 - DPS: 48 - Range: 2.50 squares - Cone: 90 degrees
The inferno targets the front enemy of the group, and any other enemies caught in its range will take equal damage. Because of their short range they are best when adjacent to the path (giving them the best cone area of affect).
Here are some good and bad inferno layouts: