Raspbian is a free operating system based on Debian GNU/Linux and optimised for the Raspberry Pi hardware (the armhf processor architecture). Raspbian comes with over 35,000 packages, or pre-compiled software bundled in a nice format for easy installation on a Raspberry Pi. The initial build was completed in June of 2012, but the distribution continues to be active developed with an emphasis on improving the stability and performance of as many Debian packages as possible. Although Debian produces a distribution for the arm architecture, it is compatible only with versions later than the one used on the Raspberry Pi (ARMv7-A CPUs and higher vs the Raspberry Pi's ARMv6 CPU). Raspbian uses PIXEL, Pi Improved Xwindows Environment, Lightweight as its main desktop environment as of the latest update. It is composed of a modified LXDE desktop environment and the Openbox stacking window manager with a new theme and few other changes. The distribution is shipped with a free copy of computer algebra program Mathematica. It also includes a version of Minecraft called Minecraft Pi and includes a Pi-enhanced version of Chromium as of the latest version.