Gdash

[altermaven]

This might be due to the reason that these cavesets may have used some unknown or benign packer that the converter cannot recognise, due to the data not exactly having parity with the tool (this could be any package that had been created before a standardized means was made available, most likely due to Assembly tinkering). It could also conflict based on the type of engine being unknown.

[CWS]

The remaining question is: how to extract the caves from that caves?

[altermaven]

I do not really know for sure. I was just making an analysis based on knowns vs. unknowns. I haven't really found the answer myself.

[BadDog73]

Does anyone know the difference between "Boulder_Dash_2_Atari.bd" and "Boulder_Dash_2_Atari.gds"?

[altermaven]

.bd is a BDCFF file, which is plaintext, whereas .gds is a compressed GDash caveset. The only difference is how GDash interprets these, and both are the same.

[CWS]

Is this really regular behavior of the Amoeba?

https://youtu.be/x_guZQiXJrA

[LogicDeLuxe]

Is this really regular behavior of the Amoeba?

It is. I designed an engine test cave covering this a long time ago:
http://www.gratissaugen.de/erbsen/exact.html

[CWS]

Thank you for the info. I haven’t thought that this would be possible…

[altermaven]

Amoeba is scanned before butterfly, but amoeba was checking if it was choked before it checked if it clashed, giving this result.

[LogicDeLuxe]

Amoeba is scanned before butterfly, but amoeba was checking if it was choked before it checked if it clashed, giving this result.

That is not the reason. The choke check can not decide to convert within the frame. It must check for expanding possibilities in the entire cave first. If the amoeba is not dormant and there are no expanding possibilities encountered at the end of frame, only then will the amoeba conversion get triggered.
It is the fact that enemies check for amoeba contact before they move. Which in this case is before the butterfly touches the amoeba. In the next line, the amoeba is blocked by the butterfly, thus expanding possibility will not get flagged here. In the next frame, the amoeba comes first in the scanning order and converts to a diamond. Then the butterfly sees the diamond and thus does not explode on it.

I exploited this in an early not that well designed cave of mine, ie. Deluxe Dash 1, Cave 11:
It is quite luck depended. If all goes well, you can exploit this trick while suffocating the other end of the amoeba with yourself. The cave can be done without freeing a firefly at all, but you have to be quite lucky to reach the exit in time. There are several annoying ways the cave will work against you, obviously.

[altermaven]

Perhaps I have worded it incorrectly but your explanation has made for a more detailed observation of why this occurs. In which I thank you for this.