skell wrote:
Okay, we wait one turn and see B. What has happened so far? Our Briar Component got larger, but the freefloating section IS NOT part of the Component. Nothing complicated is happening right now, until we wait another turn and...

E 1. Take a list of all tiles that make the component, then for every tile (FROM_TILE) do the following.
E 2. For every direction, starting with orthogonal and then diagonal (DIR will be the direction we check and TO_TILE is the position into which we're trying to grow)...
E 3. If DIR is diagonal and there was already a pit in any previous DIR for this tile, skip processing this direction.
E 4. If TO_TILE is outside room edges, skip processing
E 5. Then there is a lot of logic for checking if briar can actually grow onto TO_TILE, the most interesting of which are...
E  5.1.    If TO_TILE is pit, store a flag used in #3
E  5.2.    If TO_TILE is fluff, then FROM_TILE will become live briar, meaning Fluff is treated like a pit
E  5.3.    If TO_TILE is briar...
E   5.3.1. Freefloating withered briar, then add this briar to NEW_DEAD_BRIAR
E   5.3.2. Freefloating live briar, then add this briar to NEW_LIVE_BRIAR
E   5.3.3. Part of a different component, then add this briar to MERGE_LATER
E  5.4.    If TO_TILE is powder keg, then store it in EXPLODED_POWDER_KEGS
E  5.5.    If TO_TILE is pressure plate, store it in HELD_PLATES
E  5.6.    If TO_TILE contains a Puff, store it in KILLED_PUFFS
E 6. Cleanup time!
E  6.1. Newly grown briar, NEW_DEAD_BRIAR and NEW_LIVE_BRIAR are added to the component
E  6.2. If NEW_DEAD_BRIAR is not empty, then go back to #2 but use NEW_DEAD_BRIAR as the list of briar tiles to use

E 7. Then, when the briar component has finally stopped growing:
E  7.1. For every puff in KILLED_PUFFS, damage the briar there and kill the puff

That marks the end of single briar expansion. From the code perspective there is some more cleanup that happens later, so let me show you the overview of the whole briar processing:

P 1. If briar that's part of a component was damaged this turn, rebuild the components.
P 2. Process the briars in a way that imitates things happening simultaneously for all the briars. Essentially repeat the following:
P   2.1. For each briar source (root) try to grow its component. If there are no more live briars to grow and there is space to grow, do nothing but return information "My component wants to grow".
P   2.2. If no briar source reported growth, leave this loop and go to P#3.
P   2.3. For every briar root, do the expansion logic I outlined above
P   2.4. Iterate over MERGE_LATER from E#5.4 and merge the components at this stage. 
P 3. For every EXPLODED_POWDER KEGS from E#5.4, do the explosion now
P 4. Convert unstable tar to tar babies
P 5. For every pressure plate that was held previously and was added to HELD_PLATES in E#5.5, either activate it if it was not held down or release it if it's no longer held down

skell wrote:
5. Briar interacts with fluff similar to how it interacts with pits, except orthogonally-adjacent fluff DOES NOT prevent diagonal growth from that tile

mauvebutterfly wrote:
Are you sure about this? Fluff definitely prevents briar from growing diagonally. Maybe I'm not sure what you're trying to say here.

skell wrote:
E 5.3. If TO_TILE is briar...
E 5.3.1. Freefloating withered briar, then add this briar to NEW_DEAD_BRIAR
E 5.3.2. Freefloating live briar, then add this briar to NEW_LIVE_BRIAR
E 5.3.3. Part of a different component, then add this briar to MERGE_LATER

This is the region (32,8) - (38,10) at turn 249 (TFMurphy can beat the room by getting here a dozen turns earlier).

. Pit
_ Floor
W Withered Briar
N New Growth Briar
F Fegundo
* Explosion
A Ashes

1.
WWWWW
W.F.W
W._.W

2.
Fegundo tried to fly North.
W***W
W***W
W***W

3.
W___W
W.A.W
W._.W

4.
Briar roots are now disconnected from new growth, so it expands.
WNNNW
W.A.W
W._.W

5.
Briar roots wither 2 tiles. Should this be only one tile?
WWWNW
W.A.W
W._.W

Dragon Fogel wrote:
Briar always withers one tile after expanding.

skell wrote:
Last but not least - there is a strange consequence to how P#2 works which is easy to miss. Each component can only expand once per iteration of P#2. That's because the "convert Briar Growth to Withered Briar" step is in P#2.1 and the actual expansion is in P#2.2.

Kalin wrote:

skell wrote:
Last but not least - there is a strange consequence to how P#2 works which is easy to miss. Each component can only expand once per iteration of P#2. That's because the "convert Briar Growth to Withered Briar" step is in P#2.1 and the actual expansion is in P#2.2.

This isn't true. (Unless I'm misunderstanding what you mean by "iteration".) Briar patches can expand once per root per turn. See attached hold.

Repeat this until all roots have moved or are stuck:
    For every briar root -> Do P#2.1 and P#2.2 on that root
    For every briar root -> Do P#2.3
    Do P#2.4

Kalin wrote:
And I think something is still bugged in this step. Component A has 2 roots and 1 tile of new growth. Component B has 0 roots and lots and lots of new growth. It appears that the first root of A withers its new growth, then the second root expands it into B. Then for some reason B also expands even though it has new growth and all the roots were already processed.