Hey folks,

So it's relatively well-known at this point that hitting the 1-UP block in 4-1 sometimes allows you to grab the bottom of the flagpole without losing a framerule. That's because 4-1 normally has 6 frames of leeway, but grabbing the bottom of the pole loses 7 frames†. Spawning the 1-UP can manipulate "judges" (by the same mechanic responsible for the 8-1 judges) and give you that extra frame needed to not lose a framerule.

† (You can lose 12 frames if you grab the pole low enough. Good judges won't save you in that case :p)

What might be less known (and apologies if it's already documented somewhere and I'm just being a doofus) is where you have to hit the 1-UP block in order to get "good judges". Side note: Obviously, you shouldn't have to care about this, because you should always be grabbing the top of the flagpole anyways (or not messing up the FPG :p), but I figured that a few of you might be curious about it (if only for academic reasons), so if you're one of those people, then this post is for you. :)

Anyways: As with the 8-1 star block, there is a 4-frame "powerup rule" that affects when the 1-UP can spawn, and how the powerup rules align with the frames that you're able to hit the 1-UP block depends on the length of the black screen at the start, which is constant if you're entering from 3-4 but can vary if you're entering from 1-2. In order to get "good judges", the 1-UP needs to despawn with a y-subpixel value ($041C) at least 61.

There are 7 possible frames that the 1-UP block can be hit. Let's number them 1-7. (Actually, there's a two-frame window to hit the block on the first frame. Four frames, if you jump super early and do a small jump to hit it. For our purposes, I'm going to count these as all the same frame, since the block does get hit on the same frame.)

Here's the y-subpixel value you get from hitting the block on each of these frames ("good judges" values are bolded):

| 29 | 111 | 110 |

|...2....| 171 |

| 137 | 220 |

|..40...|...1....| 110 |

So as you can see, if you hit the 1-UP block on the last possible frame, you're guaranteed good judges. Otherwise...it depends, but generally, it seems that hitting closer to the back of the block is better than hitting the front of the block.

This can actually save runs where you try to do FPG, but end up not slowing down and you just fly onto the flagpole.

I've heard that you can also hit the mushroom to further guarantee the chance of keeping the framerule.

You can hit the mushroom to affect the powerup/flag y-subpixel, but that's a little harder to do (there's the risk of falling in the pit) and it can also possibly mess up the subpixels you get from hitting the 1-UP. I haven't tested all of the combinations, so I don't know if hitting the mushroom is overall worth it, but my gut instinct is that it's probably not.

In my experience, whether I hit the 1up block OR the mushroom block there seemed to be an equal chance of getting good judges or not (without trying manipulation) But also, if I hit BOTH the 1up block and the mushroom block, if I remember correctly, I found it would either be bad judges, or good judges turned bad (so like it's good judges but then idk what happens Mario slides down a pixel or the flag slides up a pixel)