Wiktionary
working on
vb. (present participle of work on English)
Usage examples of "working on".
Besides, he'd been working on the books, and most of that scowl probably stemmed more from his hatred for paperwork than her sudden appearance.
Athletic, potent, and fiercely energetic even in his seventies, Rumfoord has worn out four wives and is working on a fifth, his new bride Lily, who was born in the year Dresden was bombed.
He was working on improved feedback loops, something to warn me ahead of time that I was biting off more rock than I could chew.
He lives in Washington (North-East England) and is working on both short stories and full-length novels.
He's been working on the puzzle of why the dermaphos doesn't phos.