Some months ago I saw a Russian gomokunarabe player saying in an online chat to his compatriot,
А я подсел на мак.
I cannot recall the context. I can only recall that their chat looked highly colloquial and was hard to understand. They did not appear to talk about the game; the conversation seemed to be about real-life matters. The expression "подсел на мак" looked especially mysterious.
Could you explain me this mysterious expression?