Android's next great redesign is making its debut at Google I/O today. The so-called L Developer Preview follows just a few months after KitKat, but brings with it an all-encompassing visual reboot that spans the entire user experience.

There are some 5,000 new APIs in the updated software, but the big changes are primarily visual and part of Google's new Material Design initiative. There's a new Gmail interface, minimalistic new Android buttons, and a shift from square to round icons. The Google Keyboard and quick settings menu have also been updated and there are new do-not-disturb options. The system-wide Roboto font has been tweaked to work on every screen "from your watch to your laptop to your television." All of Google's stock apps will eventually make the transition to the new Material theme, however for now the list is limited to the most-used apps like the phone dialer.

Notifications are being spruced up in the new Android too, with new interactive access on the lock screen. The notification pane and the lock screen are basically being combined, with a new look that's evocative of Google Now cards. A new drop-down notification is being introduced for when you're using the phone, dubbed a "heads-up" by Google. It's big, but easy to address or dismiss. Its look will be familiar to users of LG's G3 smartphone, whose interface is designed along a similar set of circular motifs and also includes such drop-down notes for incoming calls and messages.

Google makes a big point of extending Material Design across all its software and services, including the web. Part of the I/O demo of Android L includes showing how search results on the web employ the same design language. Visual elements move across the screen and animate in the Chrome mobile browser just as they would in Android L itself, at 60 frames per second.

A stacked card overview represents recently used apps and accessed web pages. It's prettier than the current multitasking view, but might not necessarily be more efficient. It also works differently, as any individual app can throw multiple items into the list.

On the performance side of things, the new Android L will run exclusively on the Android Runtime that was introduced with KitKat. Google's Dave Burke claims it runs twice as fast as the old Dalvik runtime. It means better memory management and resource efficiency. Plus, there's the addition of an Android Extension Pack to facilitate higher-fidelity graphics on Android games, capturing the potential of powerful chips like Nvidia's Tegra K1.

The L preview code will be available for developer devices to download later today, while the full OS release is promised for the fall. Presumably that's when we'll also find out if it's actually called Lollipop or Liquorice or whatever.