Newly revealed Commander Keen 6 glitch?

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NY00123
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Newly revealed Commander Keen 6 glitch?

Post by NY00123 » Tue Mar 30, 2010 20:47

Hi all,

It's possible that a new Commander Keen glitch has just been found out. It's a bit complicated to reproduce, uses the impossible bullet trick in the way.

UPDATE: I've figured out a bit later that a bit different variant of it can reproduced on an original Keen 6 level, and not just a customized level. See a later post for details, also with pics.

In order to reproduce it, you should be in some (customized) level with:
- A pole, ending with a gem holder right below it (not far, as shown in a screen shot soon).
- Some space above the pole so you're able to impossible-bullet and later go down the pole while riding.

Here are the steps with pics:

1. Make sure you have the relevant gem for the gem holder ready.
Image

2. Trigger the impossible bullet trick right above the pole (you can do it higher if you can), and hold the "down" key.
Image

3. Keep holding the "down" key so it'd appear like you're riding down on the pole in the rate of falling.
Image

4. Now if things work as expected, you should land a bit above the gem holder and Keen would put the gem into it.
Image

5. Finally, walk a bit to the left or the right. You'd fall and go through blocking tiles!
Image


Well, first of all, about step 4, it's possible that it'd fail, and instead you'd just get stuck, not being able to move to anywhere. This case appears to not be found out for the first time, and may be reproduced without the pole. It's possible that it tries to make Keen insert the gem and, due to a clipping issue, gets stuck.

Now, if step 4 is reproduced is expected, then what does trigger the ability to go through blocking tiles? Well, on the technical side, in general, while Keen is riding a pole, "no clip" is turned on (yes just like that cheat). And when Keen lands on the holder in the middle of riding the pole, it looks like the program "forgets" to turn off "no clip", thus triggering the glitch.
Last edited by NY00123 on Wed Mar 31, 2010 19:10, edited 2 times in total.

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Post by VikingBoyBilly » Wed Mar 31, 2010 3:06

It's great to know America's economy is being saved by keeners finding impossibly obscure glitches in a 20 year old dos game ;)

Really, this is almost equivalent to that pokemon glitch one guy found where you can encounter mew in the wild by triggering arbitrary chosen but precisely executed trainer battles, flying to specific places, and going to a specific route to run into the mew.
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Post by Levellass » Wed Mar 31, 2010 10:12

I question whether this counts as a glitch as such, since it cannot be reproduced using the original levels and as such does not occur except in 'artificial' situations.

The glitch is caused because the game has certain activities that change Keen's clipping (Going through doors, climbing poles, dying...) If an activity needs to switch Keen's clipping mode, it will and there is often a provision to switch it back.

Sprites will pass through tiles if their clipping is set to 0, but will hit them if it is 2. If it is 1 then they will hit tiles, but will not be pushed out of them if they get 'inside' by accident.

Normally this doesn't cause any problem, getting on a pole turns clipping to 0, getting off it resets it to 2 A gem holder doesn't affect Keen's clipping so doesn't do anything.

Keen will use a gem holder (Or switch) automatically if he is in a position where he is using certain tile collisions. (Thus he can use one while on a board, while running, while falling, while shooting...) This is because most of the tile collisions share code, to save space, including keyholder code.

Here Keen is on a pole with clipping 0 (So he can climb through solid tiles) and using the 'floating Keen' tile collision. This lets him automatically open doors which changes his behavior to 'standing Keen' afterwards, but doesn't bother to change his clipping. (Because it shouldn't need to.) You can do something similar if you get Keen to ledgegrip over a door tile (Use animating tiles to make on appear on him when he's ledgegripping.)


On a related note, has anyone else noticed that when you're using the no clipping cheat, you can get your clipping back by falling through a floor and moving, making you ledgegrip the floor then pull yourself upright? This 'glitch' *can* be performed with the original levels in all three Keens.
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Post by Genius314 » Wed Mar 31, 2010 11:06

Levellass wrote:On a related note, has anyone else noticed that when you're using the no clipping cheat, you can get your clipping back by falling through a floor and moving, making you ledgegrip the floor then pull yourself upright? This 'glitch' *can* be performed with the original levels in all three Keens.
That's actually my preferred method for disabling no clipping! So much faster than Ctrl+N a second time.

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Post by KeenRush » Wed Mar 31, 2010 13:09

This is neat! :D How did you happen to find this in the first place?
Genius314 wrote:That's actually my preferred method for disabling no clipping! So much faster than Ctrl+N a second time.
Same here, I've always done that. Whenever I use clipping, that is. :old
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Post by NY00123 » Wed Mar 31, 2010 13:25

Well, actually, I've accidently found this out while playing a bit with a level of some level pack that has been released.

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Post by NY00123 » Wed Mar 31, 2010 15:24

ok, I've just figured out that there are, sort of, two ways to reproduce this; One explained above, the other can be done in an original Keen 6 level! And what's funny is that the latter way is what I've encountered first :lol

So, here's how it can be reproduced in level 11 (BASA):

1. Make sure you've got yellow gem. Go to the top of the pole above the yellow gem holder, jump and then shoot down at the right moment. Do NOT hold the down key for long this time, though.
Image

2. If done correctly, you should see yourself riding a bit on the shot, and then landing on the floor. For the following step, you can go a bit to the right of the pole so you're closer to the gem holder (but not too much to the right).
Image

3. Now press the down key. If everything has been working well so far, you should find yourself "warping" to a bit above the gem holder, beginning to insert the gem.
Image

4. However, it's expected that you'd fall down, with "no clip" being turned on.
Image


Note that here, the gem holder may be a bit further from the pole. That's in comparison to the previously demonstrated case.

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Post by ckguy » Wed Mar 31, 2010 21:14

Genius314 wrote:
Levellass wrote:On a related note, has anyone else noticed that when you're using the no clipping cheat, you can get your clipping back by falling through a floor and moving, making you ledgegrip the floor then pull yourself upright? This 'glitch' *can* be performed with the original levels in all three Keens.
That's actually my preferred method for disabling no clipping! So much faster than Ctrl+N a second time.
Silly Genius, I find it's actually very easy to hit Ctrl+N to disable no clipping. You just need to learn to hit the keys faster!

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Post by Roobar » Wed Mar 31, 2010 21:22

Nice! :wormouth

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Post by Levellass » Thu Apr 01, 2010 3:37

Whupp, reproducibility! We have ourselves a new glitch!
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Post by DaVince » Thu Apr 01, 2010 14:29

Ctrl+N? Oh geez, and here I have been hitting F10+N all this time... :|
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Post by Grimson » Thu Apr 01, 2010 14:39

I thought it was F10+N too :confused

I have been mislead >:
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Post by ckguy » Thu Apr 01, 2010 17:51

:o That was a typo. I make them a lot.

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Post by Genius314 » Thu Apr 01, 2010 19:42

Holy crap, I made the same typo; maybe that's where you got it from. WHAT was I thinking when I typed that. :dopekeen

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Post by DaVince » Fri Apr 02, 2010 2:45

Oh. Because everyone went with it, I honestly thought that was an alternative way of launching the cheats... :rolleyes
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