Fun, fun, fun.  I remember the first time I experienced that adrenaline rush you mention.  I was playing Evercrack... er, Everquest, back in the 90s, and took a shortcut through a zone I didn't belong in at my low 30s, and ended up fighting a lvl 50 giant.  By dint of extreme cowardice and running away a lot, I managed to beat the giant.  After that, the fun of farming giants didn't wear thin until they were no longer much of a challenge because I'd leveled up so much.

If you can make a game with that kind of adrenaline rush, I might even dust off my WASD keys and give it a crack.. er, quest or two.

Thanks!