It's a fun fangame available here. Warning: May be highly addictive.

Tips:
-Buy an Abra at the Game Corner, they are not worth it. D8
-Pikachus are difficult to catch, but useful.
-Missingno.s are unbelievably overpowered in this game. Generate a few through the Mystery Gift if a level's giving you trouble.
-Yes, Cerulean City Gym is unusually difficult.
-Remember to eat and drink. :D

Level 36 Graveler, set to Bulldoze (or Rock Blast whenever Flying Pokemon are predominant on the field)
Level 34 Kadabra, set to Confusion
Level 32 Venusaur, set to Solarbeam
Level 33 Raichu, set to Thunderbolt
Level 32 Missingo., set to Sky Atack
Level 33 Growlithe, set to Roar [in this case, level is irrelevant]

Shuffle positions as needed. I had Growlithe permanently on the innermost southeast position, Vensaur mostly on the uppermost northwest position, Missingno. mostly on the uppermost northeast position, and shuffled around Graveler, Raichu, and Kadabra as the various waves came in. Solarbeam alone will mostly take out the enemy Raichus, so Graveler is the only needed back-up there.

It's a fun game. :B