Is it 1989, or 1990? Are you at a chess tournament? Did you have an hour before your next round?
If you answered yes to these questions you are most likely playing tetris on a 2.6 screen.
I never had any issues with batteries. 4 AAs and I could go for weeks. Sadly, once I started playing Tetris, it was only days...
When I lived in Chicago, I was able to beat the entire Kirby's Dreamland before I had to get off the train (less than 45 min). I still own that game.
I occasionally take it out and play it.
I spent many a time next to the freezer hoping to get more life out of my batteries. especially when i played at night cause i would need another two for the flashlight.
The annoying clip-on lite... ugggh... but when there was no other way it was worth the misery.
The funnest game for it was Super Mario Land : G Golden coins. Tetris was a close second. But the funnest was the first time I opened it and took it apart. :)
Mega Man 4, Wario Land, Link's Awakening. Long live Game Boy