The electronic components detect the motion in space, which is 3 dimensional.  The clock is important too.  For example a half-spell, followed by a pause, then the remainder of the spell, would not work.  There has to be a clean flow of magic from the beginning of the spell to the end.  

In addition, most gesture recognition systems restrict themselves to planar sigils.  It is easiest to imagine a circle or square on a flat surface in front of you, like a chalkboard, and draw it.  Wizard Tag doesn’t care about easy!  We care about magic, so some of our spells move out of the plane and become 3-dimensional figures.  

Bystanders would see the difference between 2-D and 3-D spell casters as someone just waving their wand about and true practitioners, stepping up to the next level!

While some spells are more complex, they can all be mastered easily with a little practice!  Also, there are many low-level 2-D spells that have practical effects.

Wizards will love casting spells in 4-dimensions!