Install_D is a minimalist tower defense located in cyberspace!

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Install_D is a minimalist tower defense game located inside cyberspace! The goal is to protect your data servers from incoming computer threats such as glitches, bugs and viruses using defense programs.
Player can place towers where ever they want, creating a wide variety of defenses and strategies.
The game has 10 different types of enemies each with 3 levels of power (glitch, bug, virus, each more powerful than the last).
The player can use 6 different types of defense programs (towers) at once, each one having 5 variations, for a total of 30 different towers. Some towers are quite unique, like the web portal which places 2 portals on the map that teleport threats between them and the proxy tower which force threats to visit the proxy before reaching the server (final goal).
The game has a campaign of 40 maps, with 14 challenge maps unlocked as the player progresses. A survival mode is also available to test a player's defensive capabilities.
[Update March 13th 2014] :
-Fixed an issue where game wouldn’t load when viewed with IE 11.
-Added Sell and Upgrade keyboard shortcuts ‘s’ for sell and ‘r’ or ‘u’ for upgrade
-Web portal towers that are linked together now share the same color. This should make Portals a little easier to follow by eye.
-Shield hits from the tiny threats that spawn when a Replicating glitch is split into 4 will only destroy a single shield every couple of seconds. This should help against a single Replicating bug getting through the defenses and splitting just before the base and killing off the player. Grace period only given if there are still shields available to protect the base. If a single tiny threat reaches the base, it’s still game over.