The day you first write a "useful" program in your own instruction set is a good day to look forward to! I've been dabbling in Z80 assembly recently, and wrote

The day you first write a "useful" program in your own instruction set is a good day to look forward to! I've been dabbling in Z80 assembly recently, and wrote a program to convert lower-case input to upper-case. Not useful, but the first "real" thing I've done for 20 years in Z80.