From 944982f34a5830e94f8a68a851da0d3e707c3935 Mon Sep 17 00:00:00 2001
From: Richard Zink <Richard Zink>
Date: Wed, 7 Oct 2026 08:03:27 +0200
Subject: [PATCH] Interpolate moon position between moonrise and moonset on
 orbit

---
 index.html | 72 ++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 59 insertions(+), 13 deletions(-)

diff --git a/index.html b/index.html
index 5c17c1a..f91c8a4 100644
--- a/index.html
+++ b/index.html
@@ -363,6 +363,61 @@
             return 'M ' + sp.x + ' ' + sp.y + ' A ' + radius + ' ' + radius + ' 0 ' + largeArc + ' 1 ' + ep.x + ' ' + ep.y;
         }
 
+        function getMoonPosition(now, moonTimes) {
+            var rise = moonTimes.rise;
+            var set = moonTimes.set;
+
+            if (!rise || !set) {
+                return { point: pointOnCircle(now, MOON_ORBIT_RADIUS), isVisible: false };
+            }
+
+            // Determine if moon is visible (above horizon)
+            var isVisible;
+            if (rise <= set) {
+                isVisible = (now >= rise && now <= set);
+            } else {
+                isVisible = (now >= rise || now <= set);
+            }
+
+            if (!isVisible) {
+                // Below horizon - position based on current time (grayed out)
+                return { point: pointOnCircle(now, MOON_ORBIT_RADIUS), isVisible: false };
+            }
+
+            // Above horizon - interpolate between moonrise and moonset
+            var riseAngle = angleForTime(rise);
+            var setAngle = angleForTime(set);
+
+            // Calculate the angular difference (could be negative if crossing midnight)
+            var diff = setAngle - riseAngle;
+            // Normalize so we take the "shorter" path that matches the moon arc
+            if (diff > Math.PI) diff -= 2 * Math.PI;
+            if (diff < -Math.PI) diff += 2 * Math.PI;
+
+            // Calculate progress (0 at rise, 1 at set)
+            var progress;
+            if (rise <= set) {
+                progress = (now.getTime() - rise.getTime()) / (set.getTime() - rise.getTime());
+            } else {
+                if (now >= rise) {
+                    var endMs = set.getTime() + 24 * 3600 * 1000;
+                    progress = (now.getTime() - rise.getTime()) / (endMs - rise.getTime());
+                } else {
+                    progress = (now.getTime() + 24 * 3600 * 1000 - rise.getTime()) /
+                               (set.getTime() + 24 * 3600 * 1000 - rise.getTime());
+                }
+            }
+
+            var moonAngle = riseAngle + diff * progress;
+            return {
+                point: {
+                    x: 100 + Math.cos(moonAngle) * MOON_ORBIT_RADIUS,
+                    y: 100 + Math.sin(moonAngle) * MOON_ORBIT_RADIUS
+                },
+                isVisible: true
+            };
+        }
+
         function renderMoonPhaseIcon(phase) {
             var icon = document.getElementById('moon-phase-icon');
             icon.innerHTML = '';
@@ -481,19 +536,10 @@
             rpgSunGlow.setAttribute('opacity', isDaytime ? '0.4' : '0.15');
             rpgSunCore.setAttribute('opacity', isDaytime ? '1' : '0.35');
 
-            // Moon position
-            var moonP = pointOnCircle(now, MOON_ORBIT_RADIUS);
-            rpgMoon.setAttribute('transform', 'translate(' + moonP.x + ', ' + moonP.y + ')');
-
-            var moonVisible = false;
-            if (moonTimes.rise && moonTimes.set) {
-                if (moonTimes.rise < moonTimes.set) {
-                    moonVisible = (now >= moonTimes.rise && now <= moonTimes.set);
-                } else {
-                    moonVisible = (now >= moonTimes.rise || now <= moonTimes.set);
-                }
-            }
-            rpgMoon.setAttribute('opacity', moonVisible ? '1' : '0.35');
+            // Moon position - interpolated between moonrise and moonset on the orbit
+            var moonPos = getMoonPosition(now, moonTimes);
+            rpgMoon.setAttribute('transform', 'translate(' + moonPos.point.x + ', ' + moonPos.point.y + ')');
+            rpgMoon.setAttribute('opacity', moonPos.isVisible ? '1' : '0.35');
 
             // Sun rise/set arrows
             var srP = pointOnCircle(sunTimes.sunrise, SUN_ORBIT_RADIUS);