Hobbies And Interests
Fields of Fire
The layout of each level of Defense Grid is different and plays a major factor in the games strategy. For levels with a set path, towers should be placed to maximize the amount of time a marching alien must walk through its field of fire. Because towers fire in a complete circle, this makes towers placed at the corners of turns more effective, because the aliens must walk along two sides of the tower. Likewise, towers placed at the end of a u-turn expose the aliens to their fire for the longest time.
Open Levels
Many levels feature a mostly open grid, with the towers you build being the only way to redirect or slow alien invaders. For these levels, it is very important to construct it in such a way to force the aliens to spend the maximum amount of time on the board. This will give your towers more opportunities to wear down and destroy the aliens. Winding corridors are very effective, as they force aliens on paths that do not take them directly towards their objectives, and because they allow many towers to fire on the same aliens multiple times.
Construction
While it may be tempting to build your towers as quickly as you can in preparation for future hordes, it is generally worth it to conserve your resources. The more energy you have, the quicker you gain additional energy. Build only the towers you need to defeat the current threat, while saving as much as possible. This will give you more resources to use later in the game, when the enemies become far more difficult.
Tower Choice
Not all towers are created equal. Gun towers, the most basic tower, remain useful throughout the game, because of their cost effectiveness, overall damage and ability to upgrade. Meteor towers, which allow mortar-like coverage of large portions of the board, are also very useful because of their ability to fire where they are needed, rather than simply directly in front of them. Temporal towers, which slow down opposing forces, are excellent for creating choke points, where enemies are forced to slow down at locations with high volumes of fire. Other towers are only situationally useful. Command towers do no actual damage, but provide additional resources if enemies are destroyed within their radius. These resources generally pale, however, to the resources spent to build them in the first place. Missile towers fire only at aircraft, which can be useful if a level has a large number of airborne enemies, but as the common gun tower can also destroy aircraft, they are often redundant.
Orbital Laser
One of the weapons available later in the game is an orbital laser, a weapon that destroys any alien it touches. It is only usable several times a game, so it must be used sparingly. There are two ways to maximize its usage. One is to use it at a point where there is the largest concentration of enemies. If a level has been constructed to force enemies to backtrack, an orbital laser can often fire on two hordes of enemies: one entering and one exiting the level. The second option is to save the orbital laser for emergency usage, destroying enemies that make it through the defense grid before they can exit the level.