Tablets are nifty, but for the most part, they're built to be walled gardens; Apple is notorious for its heavy-handed curation, Microsoft plans on keeping Windows 8's Metro-style apps close to the chest, and the hot-selling Kindle Fire is a deeply tweaked and thoroughly managed variant of Android. One Linux developer hopes to make things more customizable with Spark, a Mer/KDE Plasma Active-powered tablet that's fully unlocked and open for tinkering.