Google today released its Android L developer preview, posting the download link on the official Android site.

Android L is the next major version of the Android operating system, as Google announced yesterday at its I/O 2014 developer conference. This early preview version will only run on Nexus 5 or Nexus 7 devices. Google warns that it isn’t a stable release, so you shouldn’t install it on your primary smartphone.

Android L puts a heavy emphasis on clean colors, icons, and typography. Google plans to use the same “material design” aesthetic across Chrome and other Google services.

More details from yesterday’s announcement:

Android L will also run apps on a new “ART” runtime, which replaces the Dalvik virtual machine Android previously relied on. ART will allow apps to run faster and smoother, and it’s compatible with every kind of processor, including ARM, x86, and MIPS chips. It’s also built to take advantage of 64-bit chips.

Basically, ART is a big future-proofing change for Android. Developers also don’t need to tweak their apps to support ART — they’ll simply run faster on Android L.

“We aren’t building a vertically integrated product — what we are doing is building an open platform at scale,” said Sundar Pichai, Google’s head of Android and Chrome, trying to explain why major Android updates take so long to come out.

Google announced a boatload of news at its conference yesterday. Get all the details in our I/O roundup.