Drag and drop mobile UI concept

A bit of a design & coding exercise using two colours only. I am very much a developer but like experimenting with UI Design when I get a chance :).

Saw an old video from WWDC explaining the drag and drop APIs, so I thought why not make a drag and drop keyboard?

Development done in Xcode 11.3 (Swift 5/UIKit)
Design tools: just a drawing on paper