/* M3.2.1 · Four-seasons document atmosphere v25 -------------
 * Permanent document-height seasonal atmosphere.
 *
 * Four seasonal anchors:
 *   Spring / 竹青色  #789262
 *   Summer / 霁蓝    #5B7E9C
 *   Autumn / 朱砂翮  #A63A28
 *   Winter / 天缥    #C4D7D6
 *
 * v4 refinements:
 * - Spring -> Summer is cleaner and more translucent.
 * - Autumn is warm but deliberately restrained.
 * - Autumn -> Winter passes through a pale warm-neutral bridge instead of
 *   muddy red/grey.
 * - A subtle white veil unifies the whole page and keeps cards/data readable.
 */
html:not(.embedded-page) {
    background: var(--polish-canvas);
}

html:not(.embedded-page) body {
    background:
        /* translucent white atmospheric veil */
        linear-gradient(
            180deg,
            rgba(255, 255, 255, .12) 0%,
            rgba(255, 255, 255, .18) 24%,
            rgba(255, 255, 255, .14) 48%,
            rgba(255, 255, 255, .18) 76%,
            rgba(255, 255, 255, .10) 100%
        ),

        /* main four-season continuum */
        linear-gradient(
            180deg,
            /* Spring */
            rgba(120, 146, 98, .205) 0%,
            rgba(120, 146, 98, .185) 8%,
            rgba(116, 145, 110, .170) 16%,

            /* long, clear Spring -> Summer transition */
            rgba(105, 140, 130, .158) 23%,
            rgba(94, 132, 151, .172) 31%,
            rgba(91, 126, 156, .188) 38%,
            rgba(96, 124, 153, .170) 44%,

            /* Summer -> Autumn: restrained violet-warm bridge */
            rgba(113, 111, 139, .150) 50%,
            rgba(137, 91, 106, .145) 57%,
            rgba(158, 68, 65, .150) 64%,

            /* Autumn: intentionally lighter than the original */
            rgba(166, 58, 40, .145) 69%,
            rgba(170, 82, 68, .135) 74%,

            /* Autumn -> Winter: pale warm-neutral bridge */
            rgba(179, 119, 105, .125) 79%,
            rgba(187, 156, 147, .125) 84%,
            rgba(191, 185, 180, .145) 89%,
            rgba(194, 202, 200, .185) 95%,

            /* Winter */
            rgba(196, 215, 214, .255) 100%
        ),

        /* large, low-contrast seasonal light fields */
        radial-gradient(
            ellipse at 14% 7%,
            rgba(120, 146, 98, .065),
            transparent 50%
        ),
        radial-gradient(
            ellipse at 86% 34%,
            rgba(91, 126, 156, .060),
            transparent 52%
        ),
        radial-gradient(
            ellipse at 16% 69%,
            rgba(166, 58, 40, .040),
            transparent 54%
        ),
        radial-gradient(
            ellipse at 84% 96%,
            rgba(196, 215, 214, .110),
            transparent 55%
        ),

        var(--polish-canvas);

    background-repeat: no-repeat;
    background-size: 100% 100%;
    background-attachment: scroll;
}

/* Embedded soft-navigation pages stay transparent so the shell background
 * remains continuous while navigating between sections.
 */
html.embedded-page body {
    background: transparent !important;
}

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        scroll-behavior: auto !important;
        transition-duration: .01ms !important;
        animation-duration: .01ms !important;
    }
}