Tetron2 is an icon pack. It is not a stand alone application, you need a third party launcher to apply it.

What's included:

★ 3.400 + HD icons (256x256)
★ 82 matching HD cloud wallpapers!
★ Launchers support: Action, Adw, AdwEX, Apex, Atom, Aviate, GO, Next,Nova, Smart, Solo...
★ Icon masking for un-themed icons
★ Dynamic calendar (For Nova Launcher)
★ Alternative icons to choose
★ Updates.