Looking for a nonviolent mobile game both you and your iPad-toting teen will enjoy? Download Loc, a devilishly tricky 3-D puzzler developed by Burlington-based Birnam Wood Games. The premise: You've been taken prisoner by the vengeful queen of the faeries, who wants to keep you in her kingdom. To escape, you must solve the puzzles that lie between you and freedom. Loc is a simple, block-moving puzzle game. Players shift blocks to direct a stream of green energy from a starting point along a path to the finish tile. The puzzles get progressively more challenging as you advance. Downsides: The graphics are a little dark, and because you have to move blocks around each other, it can be cumbersome to arrange the board how you want. Still, Loc will gobble up your time and give you a great mental workout. Plus, it was made by a group of Champlain College grads. Maybe it'll inspire your kids to design games instead of just play them.