It is based on the Russian Braille, with a few additional letters found in the print Ukrainian alphabet.
Ukrainian does not use all the letters of the Russian alphabet, and it has the additional letters є, ґ, і, ї.
The letter ⠽ і was once found in Russian Braille, but has been dropped.
⠜ є is the mirror image of a reported archaic form of Russian э.
(See obsolete letters of Russian Braille.)