It鈥檚 scary, but so far 
!
If you set all three rotations at once, it should be ok:
let y = rotation.y + delta.x * sensitivity
rotation = [rotation.x, y, rotation.z]
Try that!
I don鈥檛 know if you can see this thread from the Metal by Tutorials book: https://forums.kodeco.com/t/simd-badaccess-error