You're having so much fun with what you're doing that you can't see anything around you, right?
Literal
Own doing-thing [subject-が] fun [and-て] surroundings visible-not [explanatory-んですよね].
自分のやってること 'what you're doing' — casual relative clause with こと nominalizer. まわり見えてない 'can't see your surroundings' is an idiom for being so absorbed you're oblivious. The て-form of 楽しい links cause and result: 'it's so fun that...' んですよね seeks confirmation with a knowing tone.