>>50517549The early games were harder not necessarily because the fights were hard but the endurance and management was definitely tougher.
I replayed Yellow the other week, and Rock Tunnel definitely gave a run from my money. The second level is filled with trainers, you'd have definitely used up your healing items by then and there's no other market until Lavender Town. So you either fight through that level and risk fainting or go all the way back to the Pokecenter at the exit and waste repels.