Somebody asked me to explain the glitch that makes the game end abruptly. I did not explain it in the submission message, because at the time I recorded this movie, I had no idea how the glitch works. I'll try explaining it now (although it's still not crystal clear to me).
If you observe the events on the screen, you see the player using the impact of the bomb to climb upwards in the air. Shooting continuously prevents the game calculating whether the player should fall down or not, thus he stays on the air. With this bomb-trick, the player reaches the top of the level and walks off the edge of the world. He uses the invulnerability item to absorb the damage caused by falling. Then you can hear some walking and a message is triggered that says: "Your bomb has been removed." (I think that's funny.) Then the player dies.
Luckily, he got one more life to continue playing. He respawns, but the game is so messed up now that the respawn area is not defined correctly, the screen is not scrolling properly, etc. Also, who knows what kind of triggers he activated while walking outside the level? You can't tell much because the screen can't follow him.
I have not viewed any memory values to find out what's happening there, but here's an image of a part of the RAM in colors:
The upper part of the image shows the graphical data of the level layout. The middle part is the actual physical level. The yellow arrows show where I assume the player goes. The full level is not loaded yet, so the player falls through the empty part of the level into oblivion. I have no idea where the player is located now, but I assume that his position in Y-axis is quite abnormal. The screen can't follow him, so the value for the screen position may also be broken.
To make the game end requires a very precise memory overflow. If some little detail is different, the game does not end. With different movements/timing/dying, it's possible to summon level warpings, change the music, start the boss battle, mess the graphics in several ways, get super high score, trigger messages, view a naked man (No, wait, that was another window.), etc. The ending never happened without dying, so the player respawning must have something to do with it.
Alternative explanation
(That can't be the case, but I like the idea.) is that the player literally walks to the "end", into the part of the memory that stores the ending sequence. The image above shows that there's lots of data down there to dive into.
If you start a new game after the movie has ended, you can verify that the graphics and score count is badly messed up. You are awarded bonus gems for score + bonus gems for the score you get from the bonus gems, thus gaining potentially infinite score. (If you wait for a couple of hours, the score count ends.)
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Oh, eh, it seems that I'm still out of the true answer really. I also feel that I've already mentioned some of these things before. Anyway, I hope the movie makes a bit more sense now. The glitch is essentially a sequence of memory overflows, I guess.
Now that I'm at it, I must say that it would be awesome to see this movie improved by one frame.
ROM: Batman (JU) [!].gb