The title character, a partially-hatched chick, is flightless (commensurate with her species). The player assists the grounded chick through a series of 100 spike- and chasm-laden environments by creating and stretching vines with the Wii Remote or DS stylus. You first tap to create a starting point, then stretch out your new vine, and rotate it to propel Ivy forward, fixing the vine in place upon letting go. So instead of simply making platforms or inclines for her, you use the motion of the rotation to sling her into the air. Up to three vines can be onscreen at a time, and they can be grabbed in the middle, stretched, and 'snapped' to launch Ivy with even more momentum. That mechanic turns Ivy into a spinning, drill-like projectile, and can be used to fight enemies and break blocks.
This "slinging" gameplay leads to a high-speed, if graceless, trip through each level -- at first, it's hard to get the hang of drawing the lines the right way, so precision gives way to continually rushing vines on the screen to bounce Ivy forward. Once you get the hang of it, though -- as Prope head Yuji Naka and XSEED's Jimmy Soga obviously had when demonstrating the game -- the drawing maintains its speed, but Ivy's arcs become more targeted. Skilled vine drawing is encouraged by a time counter, as well as hidden bonus items in obscure or hard-to reach places.
The Wii and DS versions of the game are exactly the same in all but two respects. If you're interested in filling a living storybook with invasive vines to toss a bird about, your choice of platform will simply be a matter of whether you want the cooperative multiplayer mode (in which case you should get the Wii version), or if you don't want Yuji Naka to be able to watch over your shoulder as you embarrass yourself (in which case you opt for the DS, and also refrain from playing it in XSEED's meeting room).
Nintendo Wii console