Depending on how much time you take, you'll get 3 different conclusions, but it isn't just a matter of reaching the last boss in a certain time. The Gulf satellite takes roughly 2 or 3 hours to charge and fire, and there are two points in the game where if you go over that time, the satellite will fire. So, If you take over 3 hours to get to the Factory Area (stage 23), then you'll trigger the 1st scene. After that, if you take 2 or 3 more hours to get to the Control Center stage (stage 27), you'll trigger the second scene. To get the Good Ending, in which you fight Dan and Cecile, you can't trigger any of those scenes. To get the Normal Ending, in which you only fight Dan, you can only trigger one scene (doesn't matter which). To trigger the Bad Ending, in which you only fight Cecile, you have to trigger both scenes.