Thx Arno and Shredder!
So here we go.
Episode 1 - cuddling with fireflies!
I switched plans - at first I wanted to start with "heavy theory" and only then move on to striking effects, but now I think it's more fun to do it vice versa - first see some unexpected results of the cave-scanning order and thereby see why this issue may be interesting at all!
Our first experiment is a quite "explosive" one.
Experiment 1 - run directly into a firefly!
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D=Dirt, R=Rockford, F=Firefly
Move right in this scenario! What happens? Well...er...Rockford explodes. Wow. OK, admittedly this was rather stupid. However, there's one little thing to note - it's actually not Rockford who explodes, but the firefly!
It's the firefly who is in the centre of the 3x3 explosion. Admittedly this doesn't help Rocky much here, but let's keep it in mind and move on to our next experiment, which looks only slightly less insane!
Experiment 2 - try to walk past a firefly!
The "!" stands for "looks stupid, doesn't it?"
Let's see.
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Move right! *BOOM*
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Move left! *BOOM*
Have you actually tried it out?
If you have, then a tiny difference between the last two scenarios might not have slipped your attention. What is it? Try out and see whether you get it!
OK, so here's the tiny difference. In the first scenario, the firefly {not Rockford, as we have already noted!} explodes
immediately when you press right, while in the second scenario you see Rockford and the fly next to each other for a moment before the explosion happens. Still not too excited? OK, let's move on!
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Move up!
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What is that?
Rockford survives!! He walks past the firefly as if it was his friend, not his enemy, and the fly is free and even moves away from Rocky in order not to frighten him too much
This is by far the safest way to release a firefly that is surrounded by dirt! But how does it work? Let's see, and don't forget the basic rule from episode 0, we'll need it now!
Frame 0 - initial situation
In the scenario you can see above, the BD engine makes its usual cave-scanning. While scanning dirt is not very exciting, it becomes more interesting as soon as it comes to scanning the fly or Rockford.
1. The fly is scanned first. The engine checks whether it should explode. Rockfort does not {yet} directly touch the fly, so alright, no explosion. The engine also checks whether the fly will move, of course, but at the moment this is obviously not possible.
2. Second, Rockford is scanned and moves up because we want him to. Now Rockford is next to the fly, but the cave-scanning for this frame is already over, so still no explosion. Let's see what happens in the next frame!
Frame 1
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This looks dangerous, doesn't it? However...
1. Now Rockford is scanned first due to the cave-scanning order. The engine does note "uh-oh, there's a firefly next to you!" but remember?
It's the firefly who explodes, not Rockford! So RF does
not explode when he is scanned, and the engine asks the player what to do. We say "up", so Rockford keeps moving upwards!
2. Now it's the firefly's turn. It would explode now if Rockford was still next to it, but as RF has already moved away, there's no explosion! So the engine checks if the firefly moves. There's empty space to its left {where RF has just cleared the way} so there's a 50-50 chance whether the FF comes out immediately {this depends on the firefly's initial facing direction - let's ignore it for now and believe me it's 50-50}. Let's assume the "worst case scenario", i.e. the fly does come out immediately, which still looks threatening.
Frame 2
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Probably you already got it - Rockford still does not die despite being next to the fly!
1. RF is scanned first and we continue moving up.
2. The FF is scanned when RF has already moved out of the way. So it does not explode but turns to its left and moves downwards, because this is how fireflies behave.
Frame 3
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Clearly we're out of danger! Whoa!
Some notes to this scenario.
1. This method can be extended with as many fireflies as you like, for example
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Just move upwards - RF survives!
2. If Rockford wants to release a butterfly instead of a firefly, it is more dangerous because in frame 2 above, the butterfly would not turn to its left but to its right and thereby chase Rockford, so he would still have to find a way to escape it.
3. Placing yourself to the firefly's lower-left corner and moving up is the
only way to walk past a stationary firefly without dying. In any other case, there would be a frame where the firefly is scanned while Rockford is next to it, so it would explode. For example, let's reconsider the first two scenarios.
Scenario 1 - frame 0
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when we move right.
1. The engine scans Rockford and he moves right.
2. The engine scans the firefly. Rockford is now directly above it, so it explodes. This explains why Rockford is killed immediately here, without even a frame to spare.
Scenario 2 - Frame 0
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when we move left.
1. The FF is scanned and nothing happens.
2. Rocky is scanned and moves left. He is next to the fly now, but as the fly has already been scanned, Rockford at least survives this frame.
Frame 1
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1. The firefly is scanned. It's next to Rockford, so that's it...
So in this scenario, Rockford has survived one frame but still had no chance to escape.
Now that we've figured out the best way to cuddle with a firefly, let's consider the case that this is not possible, e.g. in the following scenario.
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How should you best release this firefly? In this case, snapping is the only method. For example, Rockford can move to the right of the firefly and snap left.
Frame 0
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1. The fly is scanned, nothing happens.
2. Rockford is scanned. We snap left.
Frame 1
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1. The fly is scanned first. It can move right and has a 50/50 chance again to do so. Let's consider it does, i.e. the worst-case scenario again.
2. RF is scanned. The FF is next to him, yet he doesn't explode, as we already know. But he has to move away immediately, or else he'll be crushed in the next frame.
So this is the "standard" method of releasing a firefly by snapping and
immediately running away. It also works from almost any other position. However, there's one way you should
not do it!
Experiment - how not to snap a fly free!
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I claim that if you snap left in this scenario, there's a 50/50 chance that Rockford dies without a chance to escape!
And this is a perfect exercise for everyone who wants to check whether he/she has understood everything!
Exercise 1 - prove my claim by checking what happens in each frame in the above scenario!
Exercise 2 - So we've just seen the worst way to snap a firefly free - but there's also a best way! Let's consider this scenario again.
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If you place Rockford in a specific point in this diagram and snap into a specific direction in frame 0, then you can even do nothing in frame 1 and only run away in frame 2 {even in the worst-case scenario that the FF comes out a.s.a.p.!} Where must Rockford be placed and in which direction must he snap?
Solutions in the next episode! Have fun!
