If there's one thing Purdue University researchers can't stand, it's an inefficient Android app. They've already revealed how some titles burn huge amounts of energy just by running ads (e.g., Angry Birds uses 63 percent of its resources for flogging stuff rather than flinging stuff), and now they've confirmed something else that has long been suspected: many offerings on Google Play also contain serious "energy bugs." Specifically, these are apps that use Android's power control or wakelock APIs to prevent a phone going into sleep mode. The majority of developers use wakelocks properly, but around a quarter make mistakes in how they juggle different APIs, which can cause a fully-charged phone to drain "in as little as five hours." Out of 187 wakelock-exploiting apps tested, 42 contained errors -- although the academics stopped short of naming and shaming. There's a chance they'll list the culprits when they present their paper next week, which will also propose an automatic method for detecting the glitches. Will that be another app?