Bullet Step trick (K6)

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KeenRush
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Bullet Step trick (K6)

Post by KeenRush » Sun Apr 06, 2014 12:53

I was just watching CapnClever's excellent Keen 6 speedrun, and what I saw around 3:12 made me ":eek" and rewind and look again (and again). Here: http://www.youtube.com/watch?v=fZyZOrhg30A

It seems like he is utilizing a pretty clever trick I don't think has been documented before. 8) I loaded up Keen 6 and got investigating. If Keen is falling, if you fire at a precise moment, you can for a split second step on the bullet, and if you're quick, you can jump off it, or even do an impossible pogo off it! If your fingers are nimble enough you can do it again after that jump, and again... About 1000 shots later, I've managed pogoing off three successive bullets shot in air. I'm still not mastering the timing -- it's garging difficult, probably a matter of 1 pixel. But it can be done (obviously), and if you become ridiculously good at it, you can get to high, inaccessible places or glide over dangerous areas without touching the ground.

I think this trick should have a name -- my proposition is Bullet Step because you as if step on the bullet for a short while.

By the way, I think many of us have noticed this collision of Keen and bullet sometime while playing Keen 6 and shooting down, but I haven't read/seen anyone figuring out to jump off it like CapnClever, or pogoing, like me. :dopekeen

Edit: It feels like it's somehow much easier to do on hard difficulty because of the slightly different physics. Maybe. Could be due to my improving at it, too.
Edit2: I think it really is the physics. Just went 4 times in a row. :)
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Post by Roobar » Sun Apr 06, 2014 13:15

Why didn't you recorded yourself doing it? I'd say Bullet Jumping or Jumpy Bullet or Impossible Bullet Jump.

That being said, in the past we had planned a mod that would rely on impossible bullet and other hard moves in order to be completed. Nothing have been done to this.

I've done this on normal. Both jump and pogo jump. That's cool once you get used to this. Still haven't succeeded in double tripple etc. jumps.

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Post by KeenRush » Sun Apr 06, 2014 14:46

Because I don't record stuff. Have no youtube channel. No video editing software. But I did anyway, now, so here's a raw DosBox recording showing triple bullet step pogo:
http://www.uploadmb.com/dw.php?id=1396792804
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Post by CapnClever » Sun Apr 06, 2014 23:15

Perhaps not documented, but it's been known for a while at least. The Commander Keen 6 TAS uses this trick extensively (and might I add ridiculously); Ma5terViking has the first recorded use on YouTube here.

There are actually three variants of moving due to the bullet collision glitch. I personally all lump them under "Impossible Bullet Trick", with other names for each type:
  • Going super-high by shooting up is what I call a rocket jump. It fits iD's other games, and a lot of people call it this anyway without knowing the name. IBT
    Using the bullet as a very temporary platform to jump off of is what I call a double jump or mid-air jump. That's ultimately what it looks like to me, and even if you can chain them, the names I mention have plenty of meaning outside of Keen games and makes the intended use more apparent.
    Shooting while hugging a wall to move Keen up just a little is what I call a step ladder. This can be chained very easily and usually ends with a rocket jump to clip somewhere: my name comes from the observation that you're "climbing up rungs from a bullet ladder".
But those are just my names: I usually just call all the tricks IBT anyway because I forget to use these monikers.

The hard part about the mid-air jump, or "bullet step" as you call it, is that the application is to gain horizontal distance. (If you need to go higher, the rocket jump is far easier.) However, you have to line yourself very precisely to propel off a moving bullet, so you have to be pretty much not moving horizontally at all. This means jumping, stopping horizontal momentum in mid-air, then jumping off the bullet. Granted it's already precise timing just to do it without going left/right, but adding that part makes the trick a great deal harder to pull off. I found that using a non-pogo jump gave me a slightly better frame window, maybe because you can buffer the command a lot easier (and don't have to bring your pogo out).

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Post by troublesomekeen » Mon Apr 07, 2014 5:28

KeenRush wrote:Because I don't record stuff. Have no youtube channel. No video editing software.
We here at BreakDownHouse Incorporated are happy to provide you with the fastest, bestest and most completest service for all your video hosting and editing needs!
http://youtu.be/gDhhQcjB_HE (for those you don't want to download)
Really cool! I didn't even know something like this was possible. :)
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Post by KeenRush » Mon Apr 07, 2014 7:52

Thanks troublesomekeen!

And CapnClever, thanks for all the info. Ohh my ignorance. :o Well, now I know better. Nevertheless, this trick is so cool. I don't think it has been used before serious speedrunning with Keen 6 started, so it's probably quite new still. Or then I've just been blind and haven't noticed.

I suddenly feel like trying to do a tool-assisted run of one of my mods. Where should I begin? :confused
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Post by NY00123 » Mon Apr 07, 2014 8:49

Keen 6 has been known to have some oddities not found in Keen 4-5, although the latter do have a variant of the IBT as well.

That's a nice take with the trick!

Now, one small question CapnClever (and/or others): In the current description of the video above, you have said that a run can be shortened by toggling on audio. For certain technical reasons, I suspect it comes to the music setting.

So, what about having a run with sound effects toggled on, but no music? I think it should have the same speed as no-audio gameplay, but actual tests are often better than theory.

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Post by CapnClever » Mon Apr 07, 2014 15:38

NY00123 wrote:Now, one small question CapnClever (and/or others): In the current description of the video above, you have said that a run can be shortened by toggling on audio. For certain technical reasons, I suspect it comes to the music setting.

So, what about having a run with sound effects toggled on, but no music? I think it should have the same speed as no-audio gameplay, but actual tests are often better than theory.
No-sound in this case refers specifically to "SFX" and not "music". The reason for the extra time is almost entirely due to start/end level jingles (apparently considered sound effects instead of music), which have to play completely before you can move on. (If you're wondering why "almost", the other time-saver is using the rocket which, again, has a forced sound clip.) I suppose I haven't checked the no-music, with-sound case, but I checked no-music, no-sound and it didn't appear to differ from with-music, no-sound.

I haven't tried this in other Keen games, but it's likely to also be the case. At the very least, in Keen4 you're able to "override" the end-level sound with the inventory pop-up/down noise, saving a little bit of time in the any% run. I'll take a quick look tonight to be sure, but it's a pretty noticeable time difference that you could eyeball it yourself.
KeenRush wrote:I suddenly feel like trying to do a tool-assisted run of one of my mods. Where should I begin? :confused
TASVideos uses an emulator called JPC-RR for its videos. It's really handy albeit requires some setup to get working, so let me know if you choose this route and have trouble getting it running. (This is what I used to figure out the Vorticon engine "air jump" timing.)

In searching for other options, I found a custom build of DOSBox that includes savestates. Go to this website and click "DOSBox SVN builds" near the top, then download for whatever platform you use. Note I haven't actually tried this myself: I will tonight because this particular function seems interesting. It could very well cause desync in recording, so I don't know if it'll be useful for a TAS.

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Post by NY00123 » Mon Apr 07, 2014 16:00

CapnClever wrote:
NY00123 wrote:Now, one small question CapnClever (and/or others): In the current description of the video above, you have said that a run can be shortened by toggling on audio. For certain technical reasons, I suspect it comes to the music setting.

So, what about having a run with sound effects toggled on, but no music? I think it should have the same speed as no-audio gameplay, but actual tests are often better than theory.
No-sound in this case refers specifically to "SFX" and not "music". The reason for the extra time is almost entirely due to start/end level jingles (apparently considered sound effects instead of music), which have to play completely before you can move on. (If you're wondering why "almost", the other time-saver is using the rocket which, again, has a forced sound clip.)
Oh, I see and agree on your examples.

As to what I've indirectly referred to, according to a few seemingly-random calculations, if there is any sense of "game ticks" then I think there are about 140.176 ticks per second with music on and 140.144 without. The additions of waits for vertical retrace may complicate this by some level, though, so tests are still better, I guess.

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Post by Levellass » Wed Apr 09, 2014 1:47

Remember now, in Keen 6 Keen's shot in like a moving Platform; anything you can do with those you can do with his shot.


Makes me want to release a puzzle pack where Keen can stand on his bullets.
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Post by CapnClever » Wed Apr 09, 2014 2:52

Levellass wrote:Makes me want to release a puzzle pack where Keen can stand on his bullets.
Heh, since you brought it up, I remembered another interesting exploit as a result of the IBT. Behold! IBT teleportation. I think this particular method of doing impossible tricks with bullets would suit a puzzle pack rather well.

EDIT: Just found the original video for this (link). Guess I'm four years late! :dead

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Post by KeenRush » Wed Apr 09, 2014 6:24

Didn't know that one either! It's been a good week for Keen tricks for me. :)
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Post by Roobar » Wed Apr 09, 2014 8:16

You missed that? I've even made some concepts and now that there's abiathar, I might even be able to make these.
viewtopic.php?t=1467&postdays=0&postorder=asc&start=0

Also, I have been thinking about something else. Levellass, will you be able to slow down a bit the speed of the bullets?

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Post by Levellass » Thu Apr 10, 2014 1:23

KeenRush wrote:Didn't know that one either! It's been a good week for Keen tricks for me. :)
Here's the thing; it CAN be used to make a working teleport. When Keen is in 'IB state' he is in essence standing on an empty sprite bracket. He will therefore be 'slaved' to the next sprite to fill that bracket. The teleport trick can be done with say gem producing blooglets, shooting enemies or, if you're very particular, item tiles.
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Post by mortimer » Thu Apr 10, 2014 10:14

No idea if this is related. But https://www.youtube.com/watch?v=jE-Rj8C8d7c
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