Ovaltine is mined on Arrakis

Basic-bitch RPG "Dragon Ruins" [Steam] could have been done on the C64. You explore an underground maze and whenever you meet monsters, they and your party auto-battle until only one side remains (or you opt to run away). Back in the starting area, you can pay to level up a character who has earnt sufficient XP for the next level, pay to level up their gear, or buy medicine or a teleporter. That's it. I'm not sure the character classes do anything. For all that, the game loop is addictive. How long will you keep pushing your luck in the dungeon, bagging precious gold, before you return to safety, spend yer hard-earned dough on improvements and save your progress? The next random encounter could be one weak critter or a group of half a dozen tough bastards you've never met before. TPKs penalise you a certain number of days before the adventuring band is resurrected, so there may be an overall time limit. Either that or the ultimate goal is to clear the maze in as few days as possible. I should probably read the instructions :-)