I was rearranging my polishes and found OPI Play 'til Midnight. I think this is one of the shades that every dark nail polish lover should have:)
OPI Play 'til Midnight is a dark ink with purple shimmer.It's not exactly a duochrome, but the color changes depending on the light from almost black to shimmery blue.
To me it is very close to OPI Ink and OPI Russian Navy.
The formula is standard for OPI polishes, it's on the thinner side. 2 coats are enough for the full opacity.