La-Mulana is two things: a profound work of art, and a monumental "screw you" to every modern game design philosophy.
The game does not ease you into experience; it demands your full attention and investment from the moment you turn it on. It then throws you, a small and powerless character, into a huge, dangerous world without any sort of guidance or sense of direction, forcing you to spend dozens of hours reading text, deciphering cryptic riddles, memorizing the map layouts, and learning the world's lore if you wish to progress.
To call the difficulty "retro" would be a disservice; the gameplay consists of all the worst parts of Castlevania backtracking, Myst puzzles, trial-and-error gameplay, and punishing NES-style platforming. Every room is filled with the most irritating enemies imaginable. The main character's controls are stiff and terrible, resembling Donkey Kong or Speulunker. You lose complete control of your movement when falling or taking damage, so one wrong jump or a hit from an enemy could knock you down several screens and force you to do everything all over again. Sometimes the game will drop you through an invisible trapdoor to the same effect, and expect you to remember where it was, or an enemy will hit you immediately after a screen transition, and you will just have to learn to enter the room from a different way next time. The gameplay can only be described as emotionally draining, and it only ever gets harder and never apologizes for itself.
The rules and physics are not even consistent, as puzzles will often involve illusionary walls, invisible platforms, unclear objectives, mysterious event flags that trigger under arbitrary conditions and don't tell you what they changed, specific items or weapons you aren't guaranteed to have discovered yet, the understanding and abuse of the minute physics of said items and weapons, rooms which wrap around to other parts of the map in non-Euclidian ways, familiar objects that don't work the way they always have, inconspicuous background decorations that are actually important, and the ever-classic instant-death traps. Your only hope to solve the puzzles, aside from just "try everything", is to look for hints that could literally be anywhere else in the entire game with no rhyme or reason to their placement. The key hint could be on a tablet you might have read hours ago in another area. Sometimes a puzzle will require a dozen hints that are literally strewn all over the entire game. Your time means absolutely nothing to the game; the game assumes you have all the time in the world to study it like a college course, practice until you can defeat erratic and unfair enemies, perform long sections of brutally frustrating platforming, and bang your head against the wall as you wander around for hours because you have no earthy idea where to go next.
If you stick with the game through all of the hardships, you will be rewarded with one of the most intricate, creepy, and powerful stories ever to be portrayed in a video game. The story starts out with perhaps hundreds of cryptic hints that will make absolutely no sense, until halfway through the game when some key revelations come to light. Suddenly, everything just clicks into place as the backstory becomes a stunning mosaic. Your mind might be blown as you realize that everything, from the position of every area, to the contents of nearly every room, to the words of every strange character and cryptic tablet, to the placement of every decoration, is there for a reason relevant to the narrative. Even the main character, as he stumbles clumsily through the cluttered and deathly labyrinths of the ruins, becomes relatable as he bears witness to the remnants of something ancient and tragic. There really is nothing else like La-Mulana's story in the way it is conveyed, and it must be experienced firsthand to be believed. It might even leave you hungering for a second playthrough just so you can breeze through the challenges with a sense of foresight and appreciate all the details you might have missed the first time.
Just be warned, it is not a game that expects you to beat it, to enjoy it, or even to play it in the first place. The motivation to push forward must come entirely from the player, as the game certainly has no regard for valuing your time or stringing you along with promises of fun and reward. But it demands to be witnessed, appreciated, and analyzed, much like a thick Shakespearean play or a picture in an art museum. If anything, it is deeply fascinating both as a work of art and as a bold statement about gameplay design, and it is highly satisfying to unravel and conquer its mysteries. But above all, it is definitely not for everybody.