I started my programming career on a TI 84+ SE. I bought it a year earlier than was required because I had friend in higher level math that had to have them and they showed my how you could program and run right on the device. My parents told me they wouldn't pay for it (it was over $100 IIRC) because I didn't need it yet but that if I did buy it they would reimburse me when I did need it. I wore the labels off the buttons of that thing (I still have it!) and the number of programs I wrote on it numbered in the 100s. I'd write games, solvers, utilities, etc, after some googling I even found some of things I actually posted online [0]. I was very active on a number of TI calculator programming forums and worked on an adventure game with my friend.
I still remember being amazed by xlib [1], a util to give you access to things only assembly programs could do in TI-BASIC. This meant you could do ALL your programming on the calculator itself but leverage things like clearing the screen, drawing a sprite, scroll the screen and more. This added capability blew my mind and I used it heavily in my development. After that I realized you could use this (very crappy, but I didn't know it at the time) "IDE" toolset from TI that ran on my computer. I remember the OS X and Windows versions didn't have feature parity and so I always liked using my friend's Mac because it was easier. Being able to code on the computer and push my code to my calculator was another huge step forward for me but I still loved being able to make tweaks on the go.
I never did jump into Z80 though, it was a little too arcane for me at the time and by this point I'd hit my 10th grade year (Sophomore in High School) and I could finally take the "Intro to Programming" class offered by my school where I learned Java. That really changed things for me, curly braces and the ability to group and abstract code crazy concepts to me but I picked them up fast enough.
I'm going to go ahead and stop here because I realize I've rambled on and this is a pretty off-topic comment as-is without me going into my history of programming.
[0] http://calcg.org/cgi-bin/files.cgi?action=autha&autha=Josh+S...
[1] http://tibasicdev.wikidot.com/xlib