I kept researching about this idea and I decided to start by creating the app design from scratch using Sketch and Illustrator. For the icons, I mainly used Google Material Design where I tweaked them to look more similar to the ones of Revolut.
I created a colour scheme with different shades of black and grey to create the dark feeling. Regarding fonts I used the San Francisco font which is the system font for iOS, macOS, tvOS, and watchOS.
I then created the mockups using Photoshop and Sketch.
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