Hardcore games do not exist
Hardcore gamers do. Any game can become hardcore depending on how it is played but there are some games more "hardcore gamer" accessible; "harder, more complicated, deep" IE: "Write me an essay"
casual games; superficial, easy to learn, shiny IE; "spell this word correctly"
as you can see the casual "word spell" can get increasingly difficult over time, but at its easiest is D-O-G, whereas the hardcore "essay" still needs to have at least 100 "D-O-G"'s