fix tracks to all be EW. no more NS tracks

docs/rules/open-questions.md

@@ -760,7 +760,14 @@ figures moved, and only because Gap 10 replaced an assumption with real numbers.
 
 ## Gap 11 — Track card orientation
 
-**Status:** DECIDED — orientation is chosen when the card is placed.
+**Status:** DECIDED — orientation is chosen when the card is placed, but the choice is **two
+rotations, not free rotation**. See the amendment at the end of this section.
+
+> **AMENDED by the 45° geometry.** Measuring `docs/tracks.png` settled what this gap was guessing at:
+> the through track is east-west across the middle of every card, there is no north-south track at
+> all, and a printed card turns 180° but never flips. So a straight has ONE orientation, and a curve
+> or turnout has two — the pair its printed handedness allows. The rest of this section is the
+> reasoning that got there, kept because it is how the decision was reached.
 
 **The problem.** Gap 4a fixed the track mix at turnout ×6, straight ×3, run-around ×3. But a track
 card has an **orientation**, and nothing says what any of them is.
@@ -824,11 +831,18 @@ to build — hard to guarantee, and easy to break whenever the deck is retuned.
 *Why not (c), rotationally symmetric cards.* It discards §A.1 entirely, one of the game's most
 characterful rules.
 
-**Implemented.** `variantsFor()` in `src/engine/track.ts` enumerates the rotations — 2 for a straight,
-6 for a turnout, 2 for a run-around — and the chosen index rides the `cardPlayed` event, so replay
-reproduces the same layout.
+**Implemented.** `variantsFor(geometry, hand)` in `src/engine/track.ts` enumerates the rotations —
+**1 for a straight** (east-west, and turning it gives the same card back) and **2 for a curve or
+turnout** (0° sends the 45° leg south, 180° sends it north). The chosen index rides the `cardPlayed`
+event, so replay reproduces the same layout.
 
-**Consequence for print-and-play.** Card art must read correctly at any rotation the card allows.
+Handedness is not a supply label: it IS the diagonal the 45° leg lies on. A left-hand card reaches
+`sw` and `ne`, a right-hand card `se` and `nw`, and two stacked cards join only when their legs share
+a diagonal. That is what makes the 4-left/4-right split of the curve and turnout supply meaningful,
+and why a run-around needs one card of each hand.
+
+**Consequence for print-and-play.** Card art must read correctly upside down — every track card is
+laid at 0° or 180°, and nothing is ever turned on its side.
 
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