Creative

Creative mode is one of the three game modes in Minecraft. It is playable in Classic and Beta 1.8.

The Creative game mode allows you to build and destroy blocks in a manner in which you can build any sort of structure you would like.

Players are given an infinite amount of most blocks to build with and no health or damage to worry about. Taking advantage of this, players can create large constructions such as castles, roads, water fountains, and much more along with forms of artwork called pixel art. Not only have users designed buildings, pixel art and caves, but also mini-sports, such as 'Spleef'. Using the current in-game features, users have put them to clever use.

Beta Creative
Beta Creative allows the player to access unlimited flying and access most of the blocks in Beta. Once a Singleplayer Creative Mode level is created, it can not be changed to a Survival world (or vice-versa) within the game, but it can be changed by editing the level.dat file inside the saves folder. In multiplayer, players can be individually changed between creative and survival mode with the /gamemode <0|1> command available to Operators. 0 being survival, 1 being creative. This means that individual players can play creative mode (at the Operator's discretion) on a survival map, or vice-versa.

In Beta Creative the inventory screen is replaced by the Item Selection Screen, which is similar to Classic Creative's item selection screen, and shows all blocks and items except Fire, Water, Lava, Mob Spawners, layers of snow and Giant Mushroom Blocks. (However, water and lava can be placed by their respective buckets infinitely, the buckets will never empty.) Dropped items can be picked up by the player, but if the hotbar is already full, the items will go in the "invisible" inventory. Even though the regular inventory where these blocks are stored cannot be accessed using any keys, it can still be accessed from the inventory box of a chest, furnace, dispenser, or brewing stand.

There is flying pre-enabled, activated by double tapping (default) and using  to go down,  to go up, and the  keys (default) to move. You can disable flying in mid-air by double-tapping again, causing you to drop to the ground.

You can pick blocks into your hotbar by pressing middle-click (default).

Mobs will still spawn like in survival (including monster spawners), and will still try to attack the player, but will do no damage. Creepers are still a hazard, as they might do damage to your structures. The player can attack mobs from a much greater distance (about 32 blocks away). Sometimes in SMP, there is a bug that makes the player unable to place blocks in the inventory, though this can be fixed by restarting Minecraft. As of Beta 1.9 Pre-release 5, aggressive mobs other than Spiders and Ghast now act as neutral to the player. Also as of the aforementioned version, the player's ability to attack far away mobs has been removed.

Normally indestructible blocks like bedrock and portals can also now be destroyed. Going too far into the Void will still kill the player, but the player can still fly around in the void provided they do not descend below the y coordinate of -64.

Before Beta 1.8 Pre-release 2, in Singleplayer, the player could control the time of day with and.

Blocks that are destroyed by means other than clicking on them (destroying a block it is attached to) can still be picked up (However, TNT, paintings, minecarts, powered minecarts and storage minecarts can be picked up when destroyed by punching).

Flying very close to the top of a block without touching it will generate footsteps sounds. As flying is way faster than walking, it will generate alot of footsteps at once. You can also hear wood footstep sounds when hovering right over some non-solid blocks like torches or signs

Representation in level.dat
To change the GameType in the  one has to decompress it with something like gunzip (rename it to   first) the open it with a Hexeditor:

You'll find the String "GameType" in clear text follewed by 0x000000:

Classic Creative
Classic Creative is available for free. It may be played by going to the Minecraft website and clicking 'Classic'.

For obvious reasons, any blocks added in Beta that were not in Classic at the time can not be accessed.