Contents
0:00 Introduction
0:20 Gravitational lensing
2:35 Gravitational potential
7:37 Refraction simulations
8:37 Gravitational index of refraction
12:11 Simulating gravitational lensing using a refractive index
13:45 Spatial refractive index vs General Relativity

Erratum:
1) The gravitational constant has a missing minus sign in the exponent. The value should be 6.7x10^-11 N.M^2.kg^-2.

The idea of a Gravitational Index of Refraction is not new. Here is a reference to a recent article by D.H.W Reffer (date unknown but after 2018):
https://vixra.org/pdf/1903.0407v2.pdf

Links to other nice videos on Refractive index:
3Blue1Brown:    • But why would light "slow down"? | Op...  
Terra Physica:    • Optical Magic: How exactly do substan...  
Looking Glass Universe:    • I don't know why light slows down in ...  

Wave simulations were made using the python scrip provided by @DiffractionLimited YouTube channel.
Link to the code download: https://github.com/0x23/WaveSimulator2D

Animation of the dancing quarks at the end of the video by "Arts at MIT".

Royalty free music used:
Cat Circus - Doug Maxwell
Always Remember to Never Forget - The Whole Other
Yoga style - Chris Haugen
Thanks very much for making this!
End tune: Floating - Early Birds

In the video, the simulations were sometimes paused to relieve the YouTube compression algorithm and the viewers' eyes a bit.

Did I forget anything? Let me know and I'll set it straight.