One way of making sure your game gets regarded as 'difficult' is the element of obscurity - if at any point we're forced to stop playing for the sake of finding out where to go next, the resultant feeling of frustration can eventually turn to positivity if the way forward then feels worth it. However there's a big difference between this obscurity in something like Dark Souls - testing you to memorise animations, level-layouts and item descriptions - and that of the second Castlevania, where the solution to a puzzle was to equip a certain item and crouch with it on the off-chance that would trigger the next section of the game. The Castlevania games have come a very long way since their initial 2D inception, with one of the most detailed - and ridiculous - lores in all of video games the likes of which is rarely talked about, although its gameplay elements like this that make the older titles very hard to return to without a walkthrough.
