About the rules page
- Updated Saturday, August 15th 2015 @ 13:33:29
Hi. The rules somewhat unclear to me.
1 "The combo-counter goes up by 1 for every line removed in succession"
But I see that this counter increased by one after every resultative round, no matter how many lines cleared
2 "A T-spin is achieved by fitting a T piece in a hole that can only be reached by a rotation ... T-spins are detected by checking if the last move was a turnleft or turnright, and 3 out of 4 corners of the T shape bounding box are occupied with blocks in the field."
This paragraph seems a bit contradictory. Firstly exists a possibility of holes that can only be reached by a rotation but only 2 corners of the bounding box will be occupied with blocks
On the other hand if 3 corners are occupied and last action was a rotation, still may be another ways to reach some holes
In this situation both conditions respected but the final state may also be achieved without rotations - Created Saturday, August 15th 2015 @ 19:05:48
After seeing this I decided to investigate a little. This is what I've established, unless of course I'm mistaken.
There are 2 algorithms for t-spin detection in general. The immobile which was the first and is the most intuitive, and the 3-corner algorithm that came after. Apparently since 3-corner has been in use the definition of what exactly is a t-spin has become somewhat unclear, or so I've read..
From the image below you can see there is quite a difference between the two algorithms.
Note there are placements which are reachable by shifts but register as a t-spin in some game releases with a "turnleft,turnright" maneuver to ensure that a rotation was the last move. I've labelled these as "not a t-spin".
13 placements are reachable only by rotation, and clear lines. Immobile detects all of them. 6 of these are detectable with 3-corner algorithm. 2 other placements are not t-spins but satisfy 3-corner.
One more thing to note is that if ever similar type spin scoring is implemented for the other 6 pieces, that would be possible with immobile, not 3 corner and it would also work just fine with wall kicks as well.
OkeyDokeyCreated Sunday, August 16th 2015 @ 10:15:36If I understood correctly, the game uses the following definition: 3 corners filled, last move was rotation. This is also the definition used in official games since 10 years at least. It has the advantage over the immobile definition that this easy to make overhang is not counted as a T-Spin: http://harddrop.com/fumen/?m115@fgH8BeG8CeH8BeI8AeI8AeI8AeI8KeF5I
You could make an additional immobile check to prevent the move in the last picture of the first post to be a T-Spin. However, rotating back and forth is usually not worth executing because it creates a hole in contrast to the standard T-Spin.
