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Peach's Castle is a tech demo for the Nintendo GameCube, distributed to various developers with the system's software development kit in 2001. The game is meant to be a demonstration for the system's graphical and rendering capabilities.
The game takes place inside of Princess Peach's Castle, which allows players to explore a series of rooms as a red arrow. From the main menu, the player has the option of selecting either the Normal Demo, allowing them to control everything, or Auto Demo, which automatically adjusts the camera's position and moves the player between rooms. By holding the B button, players can control the camera angle using the C-stick and can move the camera's position with the control stick (with the exception of the "How Many Coins?" room, which uses the X button to enable camera control). By pressing the Start button, the player can enable a number of settings, including mimmaps, rendering, debugging options, a lag meter, gamma correction, and options to toggle the music and sound effects on and off. By pressing the Y button, the player can switch between displaying the castle normally or as a wireframe.
Excluding the entrance, the castle features six rooms, each of which being meant to show off one aspect of the Nintendo GameCube's graphical abilities and can be accessed through one of five doors at the entrance. The Dome room is meant to showcase the system's ability to display large textures. The Spiral Staircase shows bump mapping and shadows. From the staircase, players can access the Hanger room, which displays antialiasing. This room also features a Warp Pipe that leads to the Cave, which uses local lighting. The Cinema room uses projection textures to display a looping video of Nintendo GameCube systems of various colors. The Metal Mario room features a statue of the character to demonstrate environment mapping. Finally, How Many Coins? features a ? Block that, when hit by pressing A, causes numerous coins to start falling, to show the maximum number of polygons the Nintendo GameCube can render.