Having the basic mechanics implemented, we can now juice it! One of my favorite VR games is the popular Audio Shield (http://audio-shield.com/). We're almost there building our own, we just need to add fireballs, a compelling environment scene, and synchronizing the fireball shots with music!
The term juice it for game design was popularized by Jonasson and Purho in their presentation talk from 2012, Juice it or lose it - a talk by Martin Jonasson & Petri Purho (https://www.youtube.com/watch?v=Fy0aCDmgnxg).
A juicy game feels alive and responds to everything you do, tons of cascading action and response for minimal user input.