Levels of uneven difficulty, which may include scripted weather events and layout transformations that negatively impact your defensive designs, unlock in a linear order. The same enemy wave compositions spawning from the same locations decrease replay value of a single level. The awkward keyboard-driven controls use an ever-present cursor in the center of the screen that is moved using the WASD keys, although you can select objects using the mouse pointer. While the enemy route indicator is a handy tool (they always follow the shortest path to the core), the interface lacks a minimap and you can’t zoom out far enough to see the entire map at one time. Alien icons also lack tool-tips so you have to memorize which weapons are best against each upcoming foe. Various tower types (gun, melee, fire, SAM, mortar, heal) can be placed in limited, pre-defined locations. Upgrades can be unlocked by completing missions, but you have to pay for the tower in addition to the more expensive upgrade; simply placing a new tower is always more efficient unless you have run out of space. Resources are earned by killing enemies and moving the mouse over cubes dropped by the fallen. A finite amount of ether can be used to heal the core or bomb a large area of enemies at once. Defense Technica borrows some concepts from previous tower defense titles and doesn’t offer much new itself, instead opting for low replay value, restrictive building, and an inefficient interface.