The Jump Save Bug (JSB) is a bug in LBA2 that lets Twinsen jump in the air indefinitely allowing him to reach places he is not supposed to reach at that point of the story.
To do it, the player must jump and save the game in mid-air. Then he must load the game, which will make Twinsen jump a little higher. Repeating this sequence can be used to gain great highs, though the process can be cumbersome.
JSB can be used, for example for the Pearl of Incandescence on Desert Island without using the proto-pack, reaching Otringal without getting arrested in the first trip to Zeelich, reaching the Secret Esmer Base in the Temple of Bù without having to make the first trip to Zeelich, or entering the GazoGem refinery's last room directly.