Press Start to pause the game. While holding Up, Left, A, B and Select, press Start to unpause the game and your ship will fly off the screen. Play resumes at the beginning of the next stage.
Configuration Mode
During the demo, hold Up and Left, then press Reset on the NES. While the screen is blank, press A, B and Select simultaneously twice. If you did all this while the screen was still blank, the "Configuration Mode" will appear.