This is a well known code. Press Up, C, Down, C, Left, C, Right, C. You will hear a tone. Hold A, then press "Start", and hold "A" until the level actually loads up.
From here, you have access to a variety of things:
- Infinite Time
- Debug Coordinates (In place of score)
- Sprite Counter (In place of time)
- Placement Mode (See below for details)
- Pause Options
- Press "A" to go back to the title screen.
- Press "B" to enable slow motion.
- Press "C" to enable frame advance.
Press "B" to enter placement mode. From there...
- Press "A" to move forward one object.
- Hold "A" and press "C" to move backward one object.
- Press "C" to place the object.