Hardcore

Hardcore mode is a game mode that is a variant of Survival, differing primarily by the lack of the abilities to respawn and change difficulty.

Features
While playing hardcore mode, the game is set to “hardcore” difficulty, which only differs from “hard” difficulty in the fact that it cannot be changed to another difficulty while playing the world

When the player dies, the game over screen only offers a button to delete the world save instead of survival mode’s or  buttons. The world save still exists until the button is pressed, leaving the opportunity for one to keep the world by using 3rd party tools. Exiting the client and loading the world again only reloads the game at the game over screen.

History
Hardcore mode was first available to the players in the 1.9 pre-release 2, and is now officially implemented in Minecraft 1.0.

The idea came to Notch from a Minecraft gameplay blog on the PCGamer site, almost a year prior.

Trivia

 * While playing hardcore mode, the heart icons of the life gauge are different.
 * In the world selection screen, Hardcore mode is written in red.
 * When a world in hardcore mode is created with the Beta 1.9 pre-release, then played with the Beta 1.8 version, the world is permanently converted into a standard survival world.
 * In hardcore mode, you actually get a score once you die, as shown in the first gallery picture.

Bugs

 * When the difficulty is set to peaceful through the options screen of either the main menu or another world, hostile mobs will not spawn with the exception of through mob spawners in the hardcore world. Adjusting the difficulty to any other setting afterwards will enable hostile mobs to spawn normally again.
 * In 1.9 prerelease 2, the "World Is Deleted Upon Death" is there when its on hardcore or not. That was fixed in 1.9 prerelease 3.