/* ===================================================================
   riron.org — Design: Scandinavian Functional / Flat Bento-Grid
   Colors: Snow #ffffff, Canvas #f5f6f8, Graphite #2d3436,
           Physics Blue #0984e3, Philosophy Green #00b894,
           Math Red #d63031, Social Amber #fdcb6e, Border #dfe6e9
   Fonts: Nunito (display), Nunito Sans (body), IBM Plex Sans (labels)
=================================================================== */

/* ---- Reset & Base -------------------------------------------- */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: 'Nunito Sans', sans-serif;
    font-size: 0.9375rem;
    font-weight: 400;
    line-height: 1.65;
    color: #2d3436;
    background-color: #f5f6f8;
    min-height: 100vh;
}

/* ---- CSS Variables ------------------------------------------- */
:root {
    --color-snow: #ffffff;
    --color-canvas: #f5f6f8;
    --color-graphite: #2d3436;
    --color-physics: #0984e3;
    --color-philosophy: #00b894;
    --color-math: #d63031;
    --color-social: #fdcb6e;
    --color-border: #dfe6e9;
    --header-height: 64px;
    --filter-bar-height: 60px;
}

/* ---- Site Header -------------------------------------------- */
#site-header {
    position: sticky;
    top: 0;
    z-index: 100;
    background-color: var(--color-snow);
    border-bottom: 1px solid var(--color-border);
    height: var(--header-height);
}

.header-inner {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 1.5rem;
    height: 100%;
    display: flex;
    align-items: center;
    gap: 1.25rem;
}

.site-brand {
    display: flex;
    align-items: baseline;
    gap: 0.5rem;
    flex-shrink: 0;
}

.site-title {
    font-family: 'Nunito', sans-serif;
    font-size: 1.25rem;
    font-weight: 800;
    color: var(--color-graphite);
    letter-spacing: -0.02em;
}

.site-kanji {
    font-family: 'Nunito', sans-serif;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-physics);
    letter-spacing: 0.01em;
}

.site-tagline {
    font-size: 0.8125rem;
    color: #636e72;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    flex: 1;
}

.header-actions {
    display: flex;
    gap: 0.5rem;
    flex-shrink: 0;
}

.action-btn {
    font-family: 'IBM Plex Sans', sans-serif;
    font-size: 0.75rem;
    font-weight: 500;
    letter-spacing: 0.03em;
    text-transform: uppercase;
    padding: 0.375rem 0.875rem;
    border-radius: 20px;
    border: 1px solid var(--color-border);
    background: transparent;
    color: var(--color-graphite);
    cursor: pointer;
    transition: border-color 150ms ease, color 150ms ease;
}

.action-btn:hover {
    border-color: var(--color-physics);
    color: var(--color-physics);
}

.action-btn--primary {
    background-color: var(--color-physics);
    border-color: var(--color-physics);
    color: var(--color-snow);
}

.action-btn--primary:hover {
    background-color: #0773c5;
    border-color: #0773c5;
    color: var(--color-snow);
}

/* ---- Sticky Filter Bar -------------------------------------- */
#filter-bar {
    position: sticky;
    top: var(--header-height);
    z-index: 90;
    background-color: var(--color-snow);
    border-bottom: 1px solid var(--color-border);
    height: var(--filter-bar-height);
}

.filter-bar-inner {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 1.5rem;
    height: 100%;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
}

.filter-bar-inner::-webkit-scrollbar {
    display: none;
}

/* ---- Filter Pills ------------------------------------------ */
.filter-pill {
    font-family: 'IBM Plex Sans', sans-serif;
    font-size: 0.75rem;
    font-weight: 500;
    letter-spacing: 0.03em;
    text-transform: uppercase;
    padding: 0.3125rem 0.875rem;
    border-radius: 20px;
    border: 1px solid var(--color-border);
    background: transparent;
    color: #636e72;
    cursor: pointer;
    white-space: nowrap;
    flex-shrink: 0;
    transition: border-color 150ms ease, background-color 150ms ease, color 150ms ease;
    display: flex;
    align-items: center;
    gap: 0.375rem;
}

.filter-pill::before {
    content: '';
    display: inline-block;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background-color: var(--dot-color, var(--color-border));
    flex-shrink: 0;
}

.filter-pill[data-domain="all"]::before {
    display: none;
}

.filter-pill:hover {
    border-color: var(--dot-color, var(--color-graphite));
    color: var(--color-graphite);
}

.filter-pill.active {
    background-color: var(--dot-color, var(--color-graphite));
    border-color: var(--dot-color, var(--color-graphite));
    color: var(--color-snow);
}

.filter-pill[data-domain="all"].active {
    background-color: var(--color-graphite);
    border-color: var(--color-graphite);
    color: var(--color-snow);
}

.filter-pill[data-domain="all"].active::before {
    display: none;
}

/* ---- Main Content / Grid ----------------------------------- */
#main-content {
    max-width: 1280px;
    margin: 0 auto;
    padding: 1.25rem 1.5rem 3rem;
}

.bento-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 0.75rem;
    grid-auto-flow: dense;
}

/* ---- Theory Cards ------------------------------------------ */
.theory-card {
    background-color: var(--color-snow);
    border: 1px solid var(--color-border);
    border-radius: 6px;
    padding: 1rem 1rem 0.875rem;
    cursor: pointer;
    transition: border-color 150ms ease;
    text-align: left;
    position: relative;
}

.theory-card:hover {
    border-color: var(--domain-color, var(--color-physics));
}

.theory-card[data-domain="physics"] {
    --domain-color: var(--color-physics);
}

.theory-card[data-domain="philosophy"] {
    --domain-color: var(--color-philosophy);
}

.theory-card[data-domain="mathematics"] {
    --domain-color: var(--color-math);
}

.theory-card[data-domain="social"] {
    --domain-color: var(--color-social);
}

.card-large {
    grid-column: span 2;
}

@media (max-width: 640px) {
    .card-large {
        grid-column: span 1;
    }
}

/* ---- Card Header ------------------------------------------- */
.card-header {
    display: flex;
    align-items: flex-start;
    gap: 0.625rem;
    margin-bottom: 0.625rem;
}

.domain-dot {
    display: block;
    width: 8px;
    height: 8px;
    border-radius: 50%;
    flex-shrink: 0;
    margin-top: 0.375rem;
}

.card-title-group {
    flex: 1;
    min-width: 0;
}

.card-title {
    font-family: 'Nunito', sans-serif;
    font-size: clamp(1.0rem, 2vw, 1.125rem);
    font-weight: 700;
    line-height: 1.3;
    color: var(--color-graphite);
    margin-bottom: 0.125rem;
}

.card-meta {
    font-family: 'IBM Plex Sans', sans-serif;
    font-size: 0.6875rem;
    font-weight: 500;
    letter-spacing: 0.03em;
    text-transform: uppercase;
    color: #b2bec3;
}

.card-chevron {
    flex-shrink: 0;
    color: #b2bec3;
    margin-top: 0.1875rem;
    transition: transform 300ms ease;
}

.theory-card[aria-expanded="true"] .card-chevron {
    transform: rotate(180deg);
}

/* ---- Card Summary ------------------------------------------ */
.card-summary {
    font-size: 0.875rem;
    line-height: 1.6;
    color: #4a5568;
    margin-bottom: 0.75rem;
}

/* ---- Card Tags --------------------------------------------- */
.card-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.375rem;
}

.tag {
    font-family: 'IBM Plex Sans', sans-serif;
    font-size: 0.6875rem;
    font-weight: 500;
    letter-spacing: 0.02em;
    text-transform: uppercase;
    padding: 0.1875rem 0.5rem;
    border-radius: 3px;
    background-color: var(--color-canvas);
    color: #636e72;
    border: 1px solid var(--color-border);
}

/* ---- Card Detail (Expandable) ------------------------------ */
.card-detail {
    overflow: hidden;
    max-height: 0;
    opacity: 0;
    transition: max-height 300ms ease-out, opacity 150ms ease 0ms;
    /* JS controls these values */
}

.card-detail.expanding {
    opacity: 0;
    transition: max-height 300ms ease-out, opacity 150ms ease 150ms;
}

.card-detail.expanded {
    opacity: 1;
}

.detail-divider {
    border: none;
    border-top: 1px solid var(--color-border);
    margin: 0.875rem 0;
}

.detail-body {
    font-size: 0.875rem;
    line-height: 1.7;
    color: #4a5568;
    margin-bottom: 0.75rem;
}

.detail-related {
    display: flex;
    flex-wrap: wrap;
    gap: 0.375rem;
    align-items: center;
    margin-top: 0.75rem;
    padding-top: 0.5rem;
    border-top: 1px solid var(--color-border);
}

.detail-label {
    font-family: 'IBM Plex Sans', sans-serif;
    font-size: 0.6875rem;
    font-weight: 500;
    letter-spacing: 0.03em;
    text-transform: uppercase;
    color: #b2bec3;
    flex-basis: 100%;
    margin-bottom: 0.125rem;
}

/* ---- Empty State ------------------------------------------- */
.empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 5rem 1.5rem;
    text-align: center;
}

.empty-illustration {
    margin-bottom: 1.5rem;
    opacity: 0.6;
}

.empty-title {
    font-family: 'Nunito', sans-serif;
    font-size: 1.125rem;
    font-weight: 700;
    color: var(--color-graphite);
    margin-bottom: 0.375rem;
}

.empty-subtitle {
    font-size: 0.875rem;
    color: #636e72;
}

/* ---- Hidden Utility ---------------------------------------- */
[hidden] {
    display: none !important;
}

/* ---- Reduced Motion ---------------------------------------- */
@media (prefers-reduced-motion: reduce) {
    .theory-card {
        transition: none;
    }
    .card-chevron {
        transition: none;
    }
    .card-detail {
        transition: none;
    }
    .filter-pill {
        transition: none;
    }
    .action-btn {
        transition: none;
    }
}

/* ---- Responsive -------------------------------------------- */
@media (max-width: 768px) {
    .site-tagline {
        display: none;
    }

    .header-inner {
        gap: 0.75rem;
    }

    .bento-grid {
        grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    }
}

@media (max-width: 480px) {
    .header-actions .action-btn:first-child {
        display: none;
    }

    #main-content {
        padding: 1rem 0.875rem 2rem;
    }

    .bento-grid {
        grid-template-columns: 1fr;
        gap: 0.625rem;
    }
}