App reviews: Stack, Stop Motion Studio

Players are encouraged to pile blocks to the sky in Stack, but it requires some pretty good reflexes. The game starts with one block on a pedestal, with another one of equal size sliding back and forth over it. It's the player's job to tap the screen at just the right moment so that the blocks match up. Get it even a little bit wrong, and the second block will cut off at the edge, leaving you with a smaller platform to deal with next time. If you get eight blocks perfectly matched in a row, the next one gets bigger. The aim of the game? Build the tallest tower you can.

It's not a complex game by any means. If you're looking for plot or interesting characters, this is not for you. But with its simple mechanics, calming color palette and soothing sound effects, Stack is a nice way to clear your mind. It is ad-supported, so those who dislike ads can pay $2 to skip them. Free, for iOS and Android devices.

Stop Motion Studio

Stop-motion animation requires concentration, patience and hard work. But it doesn't have to require fancy equipment; in fact, with this app you can just use your smartphone. Stop Motion Studio makes it easy to create your own stop-motion movies, so that you can string together photos for your own animations or time-lapse films. (It's perfect for spring science projects.) The app lets you take a series of pictures then string them together and even add audio for your own mini-films.

As a video app, this will require access to your camera. The basic app is good for creating simple shorts - or animated gifs - but if you want to get a little more fancy, you will have to spring for the optional add-on. Extra functions such as the ability to import photos from your phone's gallery, set your films on a "green screen" or to paint on your frames are up for purchase for either $5 as a pack or 99 cents per feature. Free, for iOS and Android devices.