Fix night sky too bright after sunset

Three fixes:
1. getColor() switched from 'sunPos.altitude > 0' to
   '> sunPalettes[0].alt' (-pi/2). The day palette interpolates
   through twilight to deep-below-horizon, so an hour after sunset
   (sunAlt ~ -15deg) we now stay on the day palette and get the
   intended dark 'panel' colour instead of switching to the moon
   palette immediately.
2. getNightColor() now actually applies MIN_NIGHT_BRIGHTNESS via
   shiftColor toward black (the old 'brightness' var was unused
   dead code).
3. applyWeatherTheme() cuts the weather tint by up to 70% at
   night, so a 'cloudy' theme no longer washes the night sky with
   the brighter weather sky colour.

background-final.html

@@ -1572,8 +1572,6 @@ if (useVanta && typeof VANTA !== 'undefined') {
 
         function getNightColor(moonIllum) {
             // moonIllum.fraction: 0 (new moon) to 1 (full moon)
-            // Apply minimum brightness
-            var brightness = MIN_NIGHT_BRIGHTNESS + (1 - MIN_NIGHT_BRIGHTNESS) * moonIllum.fraction;
             // Interpolate between new and full moon palette based on fraction
             var s = moonIllum.fraction;
             var c = {
@@ -1586,8 +1584,20 @@ if (useVanta && typeof VANTA !== 'undefined') {
                 sunGlare: lerpColor(window.nightPaletteNew.sunGlare, window.nightPaletteFull.sunGlare, s),
                 sunLight: lerpColor(window.nightPaletteNew.sunLight, window.nightPaletteFull.sunLight, s)
             };
-            // Apply brightness factor (relative to mid)
+            // Pull the whole night palette down by 'darkness' (a value
-            return c;
+            // 0..1 toward pure black) so new-moon skies are visibly darker
+            // than day, and full-moon skies still have some colour.
+            var darkness = 1.0 - (MIN_NIGHT_BRIGHTNESS + (1 - MIN_NIGHT_BRIGHTNESS) * s);
+            return {
+                sky: shiftColor(c.sky, -Math.round(255 * darkness * 0.6)),
+                cloud: shiftColor(c.cloud, -Math.round(255 * darkness * 0.6)),
+                light: shiftColor(c.light, -Math.round(255 * darkness * 0.6)),
+                bg: shiftColor(c.bg, -Math.round(255 * darkness * 0.6)),
+                cloudShadow: c.cloudShadow,
+                sun: c.sun,
+                sunGlare: c.sunGlare,
+                sunLight: c.sunLight
+            };
         }
 
         function getColor(t) {
@@ -1596,7 +1606,11 @@ if (useVanta && typeof VANTA !== 'undefined') {
             var sunPos = SunCalc.getPosition(now, PASSAU_LAT, PASSAU_LON);
             var moonIllum = SunCalc.getMoonIllumination(now);
 
-            if (sunPos.altitude > 0) {
+            // The day palette covers sunAlt down to sunPalettes[0].alt
+            // (-pi/2, deep below horizon). Only below that do we hand off
+            // to the moon-based night palette. This makes twilight a
+            // smooth transition through the day palette entries.
+            if (sunPos.altitude > window.sunPalettes[0].alt) {
                 return getDayColor(sunPos.altitude);
             } else {
                 return getNightColor(moonIllum);
@@ -2269,7 +2283,13 @@ window.weatherThemes = {
             var themeColors = getEffectiveThemeColors();
             if (!themeColors) return c;
 
-            var mix = 0.6;
+            // At night, weather only tints slightly - we don't want a
+            // 'cloudy' sky colour washing over deep night sky and
+            // making it look bright.
+            var _sunPos = SunCalc.getPosition(new Date(), PASSAU_LAT, PASSAU_LON);
+            var nightFactor = Math.max(0, Math.min(1, -_sunPos.altitude / 0.4));
+            var mix = 0.6 * (1 - nightFactor * 0.7);
+
             return {
                 sky: mixColor(c.sky, themeColors.skyColor, mix),
                 cloud: mixColor(c.cloud, themeColors.cloudColor, mix),

background.html

@@ -719,8 +719,6 @@ if (useVanta && typeof VANTA !== 'undefined') {
 
         function getNightColor(moonIllum) {
             // moonIllum.fraction: 0 (new moon) to 1 (full moon)
-            // Apply minimum brightness
-            var brightness = MIN_NIGHT_BRIGHTNESS + (1 - MIN_NIGHT_BRIGHTNESS) * moonIllum.fraction;
             // Interpolate between new and full moon palette based on fraction
             var s = moonIllum.fraction;
             var c = {
@@ -733,8 +731,20 @@ if (useVanta && typeof VANTA !== 'undefined') {
                 sunGlare: lerpColor(window.nightPaletteNew.sunGlare, window.nightPaletteFull.sunGlare, s),
                 sunLight: lerpColor(window.nightPaletteNew.sunLight, window.nightPaletteFull.sunLight, s)
             };
-            // Apply brightness factor (relative to mid)
+            // Pull the whole night palette down by 'darkness' (a value
-            return c;
+            // 0..1 toward pure black) so new-moon skies are visibly darker
+            // than day, and full-moon skies still have some colour.
+            var darkness = 1.0 - (MIN_NIGHT_BRIGHTNESS + (1 - MIN_NIGHT_BRIGHTNESS) * s);
+            return {
+                sky: shiftColor(c.sky, -Math.round(255 * darkness * 0.6)),
+                cloud: shiftColor(c.cloud, -Math.round(255 * darkness * 0.6)),
+                light: shiftColor(c.light, -Math.round(255 * darkness * 0.6)),
+                bg: shiftColor(c.bg, -Math.round(255 * darkness * 0.6)),
+                cloudShadow: c.cloudShadow,
+                sun: c.sun,
+                sunGlare: c.sunGlare,
+                sunLight: c.sunLight
+            };
         }
 
         function getColor(t) {
@@ -743,7 +753,11 @@ if (useVanta && typeof VANTA !== 'undefined') {
             var sunPos = SunCalc.getPosition(now, PASSAU_LAT, PASSAU_LON);
             var moonIllum = SunCalc.getMoonIllumination(now);
 
-            if (sunPos.altitude > 0) {
+            // The day palette covers sunAlt down to sunPalettes[0].alt
+            // (-pi/2, deep below horizon). Only below that do we hand off
+            // to the moon-based night palette. This makes twilight a
+            // smooth transition through the day palette entries.
+            if (sunPos.altitude > window.sunPalettes[0].alt) {
                 return getDayColor(sunPos.altitude);
             } else {
                 return getNightColor(moonIllum);
@@ -1416,7 +1430,13 @@ window.weatherThemes = {
             var themeColors = getEffectiveThemeColors();
             if (!themeColors) return c;
 
-            var mix = 0.6;
+            // At night, weather only tints slightly - we don't want a
+            // 'cloudy' sky colour washing over deep night sky and
+            // making it look bright.
+            var _sunPos = SunCalc.getPosition(new Date(), PASSAU_LAT, PASSAU_LON);
+            var nightFactor = Math.max(0, Math.min(1, -_sunPos.altitude / 0.4));
+            var mix = 0.6 * (1 - nightFactor * 0.7);
+
             return {
                 sky: mixColor(c.sky, themeColors.skyColor, mix),
                 cloud: mixColor(c.cloud, themeColors.cloudColor, mix),