Alternate building animation - even/odd heights grow/shrink opposite

index.html

@@ -5337,16 +5337,22 @@
         function animateBuildings(timestamp) {
             if (!buildingAnimationEnabled) return;
 
-            // Single multiplier for all buildings: 100% to 150%
-            // (sin + 1) gives 0 to 2, multiply by 0.25 gives 0 to 0.5, add 1 gives 1.0 to 1.5
-            const multiplier = 1 + (Math.sin(timestamp * buildingAnimationSpeed) + 1) * 0.25;
+            // Two multipliers 180° out of phase: when one grows, the other shrinks
+            // Range: 100% to 150%
+            const sinVal = Math.sin(timestamp * buildingAnimationSpeed);
+            const multiplierA = 1 + (sinVal + 1) * 0.25;      // 1.0 → 1.5
+            const multiplierB = 1 + (-sinVal + 1) * 0.25;     // 1.5 → 1.0 (inverted)
 
-            // Update building height
+            // Alternate based on floor of height being even/odd
             if (map.getLayer('buildings-3d')) {
                 map.setPaintProperty('buildings-3d', 'fill-extrusion-height', [
                     '*',
                     ['get', 'render_height'],
-                    multiplier
+                    ['case',
+                        ['==', ['%', ['floor', ['get', 'render_height']], 2], 0],
+                        multiplierA,
+                        multiplierB
+                    ]
                 ]);
             }