99/4A Sprites!
I had a 99/4A as my 2nd or 3rd computer (I don't remember if I had it right before or after the OSI C1P but it was after the Netronics 1802 Elf). I totally loved the advanced graphics ability it had, using sprites as independent objects. But the cost of the expansion chassis and modules prevented me from hanging on to it for very long. For years afterward I used other peoples mainframes via Hazeltine 1420 or LSI Adm3A terminals until I managed to get a Mac IIx with A/UX