优化分布

public/js/app.js

@@ -977,16 +977,22 @@
           const isForward = (start === pts[0]);
 
           // Calculate curveness: ensure all lines are slightly curved
+          // Use a canonical hash of the route endpoints to deterministically decide the curve direction
+          // This helps spread lines across the map even for single routes
+          const names = [route.source, route.dest].sort();
+          const routeHash = (names[0] + names[1]).split('').reduce((acc, char) => acc + char.charCodeAt(0), 0);
+          const baseSign = (routeHash % 2 === 0 ? 1 : -1);
+
           let finalCurve = 0;
           if (count === 1) {
-            finalCurve = 0.15; // Default slight curve for single lines
+            // Single lines get a decent curve, alternating direction based on hash
+            finalCurve = 0.2 * baseSign;
           } else {
-            // Spread overlapping lines: 0.15, -0.15, 0.3, -0.3...
-            // This creates an "eye" or "fan" effect where no line is straight
-            const magnitude = 0.15 + Math.floor(i / 2) * 0.15;
+            // Multiple lines between same points fan out with increasing magnitude
+            const magnitude = 0.2 + Math.floor(i / 2) * 0.15;
             const spread = (i % 2 === 0) ? magnitude : -magnitude;
-            // Adjust sign based on direction so they occupy unique visual slots
-            finalCurve = isForward ? spread : -spread;
+            // Apply baseSign to ensure the whole group isn't biased to one side
+            finalCurve = isForward ? (spread * baseSign) : (-spread * baseSign);
           }
 
           finalSeries.push({