King's 10pb Underflow Notes

From Kingofthehill476

13% Ice-Pb is made possible by underflowing ammo at draygon with only 10 pbs. However, this requires laying a pb frame perfectly and then collecting a pb drop from goop (a 2-frame window). Thus, it takes both luck and skill to complete a run.

My solution aims to mitigate the RNG working against you and increase the skill component. Within the small RNG loop, I didn't grind for a 2 in 87 chance for a pb drop. I grinded for a 4 in 43 chance of a goop pattern that I know will result in a pb drop at the right time. This essentially normalizes goop shot timing and pb placement timing while increasing the odds of encountering the desired RNG (goop patterns).

Short Answer

1) Enter a tiny RNG loop with 87 RNG values compared to the normal 2200+ values. Here's how to do it:

• Save your game outside of Norfair (Not quite anywhere outside of Norfair, but saving in tube, aqueduct or pre-dray will definitely work)
• Get down to 69 health
• Walk into pre-cathedral from the left with suits off
• Don’t move in the room. Sit there and die
• Load your save. As long as you don’t get to the title screen (resetting) or go to acid rooms, then you’ll still be in the loop. This means that you need to die and select continue after any failed attempts
• Subunit health must be at 0x00, so pause abusing and refilling health from reserves will set it to this.

2) Recognize workable patterns. There are 4 that I identified and I'm sure there's other ways to do it. Also, 43 out of the 87 RNG values are goop values, so it should actually be 4 in 43 (1 in 10.75, or a 9% chance) of getting a workable pattern rather than 4 in 87. Here are the setups I found before completing the run: [1] [2] [3] [4] These patterns are characterized by the 4th goop (or the 5th in the third video) being just above samus's arm.

• However, turrets also advance RNG forward 1 frame every 64 frames (even when destroyed). This may slightly change one goop angle (which might've happened with the 3rd goop in the 2nd setup but I could be wrong). Still, I found during my run that most goop patterns that ended up with the 4th and one pattern with the 5th goop at the right height ended up being workable. Anything else was not a workable pattern (at least with my setup). I don't know much about this, but Strotlog said it could be a 10% chance that this affects the goop angle in a way that throws off what would otherwise be a workable pattern.

3) Time the goop shot accordingly. The 2 RNG values that drop a pb are back-to-back, meaning it's a 2-frame window to shoot the goop. I believe this is based on the timing of when the first goop appears (or when the second one appears in the 3rd setup). When it appears later, it should be shot later. One pattern with the 4th goop at the right height would drop a pb just out of reach (too early), which one could tell because the 1st goop appears significantly earlier. There's also a small chance that turrets could skip one of the pb drop values, essentially making it a frame-perfect goop shot.

4) Time the frame-perfect pb placement accurately. In my opinion, this is the hardest part of the setup, and the part I know the least about. Draygon's position relative to pb placement timing seems to be +/- 1 pixel across the setups. I've attached images that show the frame when the pb needs to be placed in multiple setups. If all the steps are mastered except for this, then all that has to fall into place would be getting a workable pattern (1 in 10.75) and placing the pb at the right frame (let's say 1 in 4). [5]