They are not kidding when they say "needs a smooth flat surface." This is best suited for kamikaze ankle-attack runs either indoor, or on a tennis/basketball court (during a match, just to spice things up). Even slight uphills, sidewalk cracks, and curbs will confound it's magical mechanics, rendering the kid-energy-expending device less effective at expending energy, and more effective at forcing parents to stoop down at back breaking angles to push the thing. Downhills also become fantastic physics demonstrations underscoring why tricycle-like three-wheel designs are inherently unstable at speed, featuring your kid as the test dummy (painting checkered markers on joints and appendages is optional, though very rewarding if filming).
The kid will love it regardless, even if she just goes around the dining room table, she will go around that table for an hour. 60 minutes of calorie-burning, parent-getting-$#!t-done goodness.