Unwinnable by Design/Playing With

Basic Trope: A situation where Video Game designers deliberately include a way or ways to make the game Unwinnable.
 * Straight: Albert has to find the legendary gear of the great hero Miran. It's possible for him to miss collecting the Pendant of Power or Gauntlets of Greatness before the areas where they are hidden are destroyed by Marduk. If this occurs, the game is rendered Unwinnable.
 * Exaggerated: Albert is supposed to gather four other Chosen Ones and all of the legendary equipment in order to face Marduk. It is, however, entirely possible to miss recruiting Princess Velvet or Pike, or to destroy a Load Bearing Boss without realizing that one of the legendary treasures is still hidden deep inside the dungeon you just wiped out. This makes the game Unwinnable.
 * Downplayed: Missing an item makes a whole side-quest unwinnable, but not the main plot
 * Justified: The game is one of those weird ones where the point of the game is to deliberately avoid the unwinnable game state.
 * It's a Sierra game
 * Inverted: Winning the game is inevitable.
 * Subverted: When a plot item is destroyed, it appears somewhere else.
 * You can miss the Ultimate Mon - Apollo for Albert, Hades for Marco, Venus for Princess Velvet, Artemis for Celeste, and Chronos for Pike. They're the effect, not the cause.
 * Double Subverted: ...except for one.
 * They're the cause of something else.
 * Parodied: Charlie is playing BobQuest, and his first mission is for Bob to deliver Alice's lunch. He has Bob eat her lunch instead, rendering the game Unwinnable.
 * Alternately, the game has an "Impossible" difficulty setting...which is Exactly What It Says On the Tin, as described in the main article.
 * Deconstructed: The game gets panned by critics for its sadistic difficulty, and it suffers a reduction in sales because of it.
 * Reconstructed: People somehow enjoy it?
 * Zig Zagged: The player is told flat-out that Albert needs to recruit the other Chosen Ones and warned that the legendary equipment is well-hidden and may be "Lost Forever to the sands of time" if they aren't careful. It's also impossible to miss recruiting Marco or Celeste, and several warnings are given whenever the player is about to potentially bypass a vital item. On the other hand, Velvet is difficult to read and doesn't officially join until late-game, and only if treated well, while Pike can be Killed Off for Real without the player even realizing you can rescue and recruit him, and other equipment can be accidentally missed.
 * Averted: There is no way for the player to accidentally miss something important and make the game impossible for them to win.
 * Enforced: The designers want players to pay more attention to the world they've created, so they make it that a player who isn't paying attention will stumble into one of these traps and screw themselves over without realizing it.
 * Lampshaded: The game in a bit of niceness, causes the save points to refuse to save for you after a MacGuffin is destroyed, stating "You cannot win, assisting you now would be cruel."
 * Invoked: Marduk is Dangerously Genre Savvy and is deliberately hiding some of the legendary equipment in dungeons with Load Bearing Bosses so that Albert might accidentally make it impossible for him to retrieve, making the prophecy impossible to fulfill.
 * Defied: The game has entered a known unwinnable state, but some glitch or trick is used to beat the game anyway.
 * Alternatively, they made the player able to go back and get what they need.
 * Discussed: "It's from Sierra, half the fun is finding new and improved ways to screw up."
 * Conversed: ???
 * Played For Laughs: You can get a quasi-Nonstandard Game Over by throwing the key to the pyramids into the lava. Your party members berate you for being mind-numbingly stupid and leave you in a hilarious cut scene. This scene becomes a favorite amongst gamers.
 * Played For Drama: Making the game unwinnable requires sacrificing Albert's little sister Beth to get a sword of invulnerability, otherwise known as the Coward's Sword. The only thing left to do in the save file is to listen to everyone yell at you in disgust. Even Marduk is appalled.

Did you click that link? Crap now you can't head back to Unwinnable By Design for the final boss.