The most challenging game I have ever played was Demon Souls on PS3. When I first bought it I played for about 90 minutes and swore to myself that I would never play it again. I'm really glad that I gave it another go a couple of months later...it is challenging in the sense that you must be focused and determined at all times. It takes very little to kill your character, which happens very often before you push yourself far enough up the steep learning curve, and when you die all of your precious souls gained from slaying corrupted inhabitants of widely varying environments and used for equipment repairs and purchases (and leveling your character I think) are left as a coloured smudge on the ground for you to collect...after walking all the way from the beginning of the level, and only to face the beastie that made you a stain on the ground again...and again...and again...and from memory I think you lose half of your HP when you die and have to return from heaven...so the game pulverizes you, takes all of your currency, leaves you with your battered belongings, and makes your character twice as easy to kill...and makes you walk from the beginning of the level no matter how close you were to the end...only to make it clear again that you are not worthy...
But don't give in to this sadistic hell spawn of a game...you will form the belief that it would be far more enjoyable to hit yourself in the groin with a heavy stick repetitively than play this game...but should you perservere and prove yourself a worthy hero...you will truly feel like one! Battle deep into the game and you will discover amazing tactics to deal punishment and judgment out to your foes...great weapons to impale bad guys with...stunningly beautiful and lovingly crafted environments that draw you into a game so immersive you can feel the chill of the cold grey environments, almost feel the maggots squirm under foot in the green disease filled sewers, and find it impossible to enjoy the warmth that a seemingly more hospitable environment can afford you with a radiant glowing sun. The story and characters are as surreal as the environments, and once you are finished with the game, or the game is finished with you, no game will ever measure up as you will never feel as connected to a character, as immersed in a game world, or as challenged again...unless the sequel proves to be equally a product of hell.
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"Have you got it, yet?..."
Syd Barrett