A grand and intense tower defense science fiction game, where you only need to purchase once to enjoy all the content of the game. Features 21 storyline chapters that tell the story of our war with "us" from parallel worlds, with over 50 hours of experience in the storyline mode Building a powerful firepower defense network in 21 3D scenes with different terrains to resist the enemy's crazy attacks 3 game modes to choose from, each full score clearance will have challenges 8 different types of firepower towers, 4 different types of firepower support, as well as 15 enemy ground vehicles and 5 types of aircraft. Resist attacks from over 3000 enemy vehicles and aircraft in one level, and enjoy the thrill of elimination in intense combat games to the fullest

Go to: http://store.steampowered.com/ and download STEAM client Click "Install Steam" (from the upper right corner) Install and start application, login with your Account name and Password (create one if you don't have). Please follow these instructions to activate a new retail purchase on Steam: Launch Steam and log into your Steam account. Click the Games Menu. Choose Activate a Product on Steam... Follow the onscreen instructions to complete the process. After successful code verification go to the "LIBRARY" tab and start downloading.