优化布局

public/js/app.js

@@ -803,14 +803,16 @@
                 const pts = [start, end].slice().sort((a, b) => a[0] - b[0] || a[1] - b[1]);
                 const isForward = (start === pts[0]);
                 
-                // Calculate curveness spread
+                // Calculate curveness: ensure all lines are slightly curved
                 let finalCurve = 0;
-                if (count > 1) {
-                    // Spread curveness between -0.3 and 0.3
-                    const maxSpread = 0.3;
-                    const spread = (i - (count - 1) / 2) * (maxSpread * 2 / Math.max(1, count - 1));
-                    // Adjust sign based on direction so same "slot" arches same way in absolute terms
-                    // A->B with curve C and B->A with curve -C arch to the same side of the AB chord
+                if (count === 1) {
+                    finalCurve = 0.15; // Default slight curve for single lines
+                } 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;
+                    const spread = (i % 2 === 0) ? magnitude : -magnitude;
+                    // Adjust sign based on direction so they occupy unique visual slots
                     finalCurve = isForward ? spread : -spread;
                 }