Click-and-Drag: Free-rotate Arrows: Rotate @ 150°/s (5° per frame) WSAD: Rotate @ 30°/s (1° per frame) Space: Reset to 0° (No Z-rotation implemented)
Originally for practicing geometry, it then became a practice of Matrice multiplication. Formula derived from: https://en.wikipedia.org/wiki/Rotation_matrix?oldid=944598131