Dungeon Crawl Stone Soup is the definition of tough but fair for me. It's a turn based game though, so not much controls to speak of. In fact because it traces it's lineage back to the 90s it's kind of clunky. But since it's turn based you can pick up and drop any time you want. Depending on my luck and skills a run lasts from 5 seconds (lol) to an hour ish.