Actually,

ZTetris and Ztris also had multiplayers. It was impossible to play from 83+SE to 83+, tho

That's funny.  I've never had problems with Ztris and 83+'s 84+'s 84+se's.  I link play with those all the time.
(My earlier question seems to have been answered- It's like Ztris.)

yeah true, that'S one thing these two games didn't have

A bit of an update: Brought the game to school.  It works for the most part between all combinations of 83+ family calculators using i/o.  I still don't kniow about usb, however; I'll have  to try that another time.  So far the only bug I've found is that it hangs on the entrance screen 1 in 20 times, but I know why and I can fix it.  Look forward to a beta release very soon.

Eeems: Because I'm an idiot and mixed up my local labels so I thought there was a loop checking for a keypress, but there wasn't.

bump