My intelligence level at the age of 14 was that I could finish Myst and loved it, but not Riven and had to buy a guide to help me with it. I think it might be the only game I bought a guide for. Never got over that.
Actually, I did phone the super mario 64 help hotline as I was missing level 10. 60p a minute!
Same. Riven was such a massive step up in difficulty from Myst.
Of all the 4 games (yes 4, I refuse to acknowledge the last entry) it is definitely the most difficult. I had to wait for it to come out on GoG and replay it as an adult to finish it.
Actually, I did phone the super mario 64 help hotline as I was missing level 10. 60p a minute!