I'm not sure Sudoku Wallet is mixer, since they claim they don't have control over your Bitcoin and use CoinJoin.
P.S. I know they're not being transparent about their system and currently closed-source.
You're correct about them closing their source but the wallet in subject claim to be bitcoin mixing wallet and i also believe they are not been honest when they claim not to have control over the transaction done on their platform when all mixing company dies that..
And they also mention that they use CoinJoin and have temporary wallet functionally, which makes us more confusing whether it's classified as mixer or CoinJoin service.