AVOKIDDO injects a bit of science into apps for kids. Their DNA Play introduced the concept of  mutability as viewers control the gene sequence of a creature, creating and altering its features and shape. A new production was recently rolled out. Paula Willey reviews it below.   Thinkrolls: Kings and Queens (AVOKIDDO, iOS, $3.99; Android, $3.99; K- Gr 6) is stimulating, but not impossible, moves quickly and builds on itself, and, best of all, is populated by little round characters who emit a wide range of nonverbal squeaks, giggles, coos, and chirps. The app has a brief learning ramp-up and, like the World of Goo (another puzzler), demonstrates basic concepts of physics. Simple machines, force, and reflection are all used to clear a path as viewers roll and drop characters along paths and across bridges through a series of castles. Sequence is especially important in order to solve these puzzles. Wooden chests can fill in holes, break through bridges, or serve as platforms. Gears must be deployed strategically to give a character access to a key and a doorway on each level. But gamers must watch out for farting ghosts and growling crocodiles! They can also pick up sweets and gems that a large, friendly dragon vacuums up in exchange for additional accessories—tresses, headwear, and facial hair that can be added and combined, as in Mr. Potato Head. Also like World of Goo, the graphics are fairly simple, witty, and executed in toothsome color palettes. Contributing to the marvelous aesthetic quality of this game, a light, sweet orchestral soundtrack accompanies players' progress. Lots of plucked strings, harp, flute, and piano, and enough recorded segments are heard that the music never becomes stale. Kids can play as a beginner or play at the "hard" setting—the levels are short, so if players get stuck, a tap to an arrow will return them to a spot where they can give it another try—as often as necessary . There are no time limits, and both the "easy" and more difficult mode contain more than 100 levels, guaranteeing return visits. A trailer is available. VERDICT Castles await players in a stimulating game incorporating logic, physics, fantasy, and fun.—Paula Willey, UNADULTERATED.US  

Screen from Thinkrolls: Kings & Queens (AVOKIDDO)