A bit late to the party, but I'd like to insert my opinion after seeing so many adult game devs wanting to force a hard mode onto their players.
While I personally don't mind hard games, you have to make sure you game follows a smooth difficulty curve to give the player some time to adjust to your game's mechanics and allow him to experiment with what he can and cannot do.
People like to thrash Pokemon games for being easy kiddy games, but if there is one thing those games do well is teaching their mechanics. Every game (especially Black And White) really, REALLY wants to make sure you've learned and understood every essential game mechanic the game throws at you. Very early on and until roughtly half of the game, you will hear NPCs talk about abilities, healing and held items, team composition, reproduction, etc... And while they don't ask you to use all of those mechanics, they are taught well enough that even the most casual of players will start looking into what item would be best for their pokemons, or what pokemon they should replace for the next gym badge. The difficulty might not be high, but the difficulty curve to reach that height is very well balanced in my opinion.
As for porn games, I really, really hate when devs neglect the difficulty curve and just throw you into a level where they ask you to use every mechanic they conceived at once or you've lost. This is especially bad when a keyboard layout is used, since devs typically put a ton of commands on a lot of keys that change constantly depending on the user's keyboard localization or the language locale they set for their computer. Some games on this site allow you to rebind your controls, but that's not enough in my opinion.
LonaRPG is a pretty good culprit of this. The game doesn't teach you evey mechanic in its tutorial, and then throws you into a level with a lot of commands and sub-systems you have to manage, while fighting enemies way faster and stronger than you and where any single mistake can ruin your run. There is a real problem with this game's difficulty when your players struggle to even pass the tutorial level. Like, you know, the easiest level in any game ever ?
So if you want a hard game, fine, but be careful not to neglect your tutorials and your difficulty curve. I've stopped playing many great games halfway through (or even after the first level) just because of an annoying boss or swarm of enemies that just keep one-shotting me at every run. Also, I know this is kind of a joke in this community but... Making games playable with one hand is a real thing. Most adult games are easy because they are porn games, which is the carrot at the end of the stick for those games, not the stick itself.