Hello folks,
   
I have some questions regarding TI and programming games on calculator.

In fact, I'm an "old man" who don't touched a calculator since the end of high school or 10 years ago, and I am interested in programming games (typically RPG).

I'm looking for a development platform that would be like 8-bit computers of the time, ie provided with programming languages and programmable directly above , like in the bus (without using a computer fixed).

Specifically, graphical calculators seems appropriate.
Know that I have a HP49 and I wonder if TI would not be better (TI-Basic and xlib).

So what would be the best IT for such use?
A TI89 necessary?
A TI8 sufficient? The 83 programs operating there on 84?

Thank you for your clarification.