/* ============================================================
   THEME VARIABLES — LIGHT (default)
   Thin sapphire glass — ultra-clear, high transmission
   ============================================================ */
:root {
    --bg-primary: linear-gradient(135deg, #f8f9fd 0%, #f2f0fa 25%, #f6f2fb 50%, #f0f4fd 75%, #f8f9fd 100%);
    --text-primary: #1a1a2e;
    --text-secondary: rgba(26,26,46,0.45);
    --text-muted: rgba(26,26,46,0.28);

    /* Sapphire glass — high transmission, minimal fog */
    --glass-bg: rgba(255,255,255,0.06);
    --glass-bg-strong: rgba(255,255,255,0.12);
    --glass-bg-subtle: rgba(255,255,255,0.03);
    --glass-border: rgba(255,255,255,0.18);
    --glass-border-light: rgba(255,255,255,0.10);
    --glass-glow: rgba(255,255,255,0.06);
    --glass-inner-highlight: rgba(255,255,255,0.12);
    --glass-shadow: rgba(0,0,0,0.02);
    --glass-shadow-heavy: rgba(0,0,0,0.04);

    /* Element cell — sapphire thin */
    --cell-bg: rgba(255,255,255,0.05);
    --cell-border: rgba(255,255,255,0.15);
    --cell-hover-shadow: rgba(0,0,0,0.03), 0 0 16px rgba(255,255,255,0.08);

    /* Overlay */
    --overlay-bg: rgba(255,255,255,0.08);

    /* Detail panel — crystal clear */
    --detail-bg: rgba(255,255,255,0.10);
    --detail-header-border: rgba(255,255,255,0.12);
    --detail-row-bg: rgba(255,255,255,0.06);
    --detail-row-border: rgba(255,255,255,0.10);

    /* Atom viewer */
    --atom-bg: linear-gradient(135deg, rgba(248,249,253,0.15), rgba(246,242,251,0.15));

    /* Badge */
    --badge-bg: rgba(255,255,255,0.10);

    /* Toggle button */
    --toggle-bg: rgba(255,255,255,0.08);
    --toggle-border: rgba(255,255,255,0.15);

    /* Title gradient */
    --title-gradient: linear-gradient(135deg, #0d9488, #0891b2, #3b82f6);

    /* Transition */
    --theme-speed: 0.5s;
}

/* ============================================================
   THEME VARIABLES — DARK
   ============================================================ */
[data-theme="dark"] {
    --bg-primary: linear-gradient(135deg, #0a0a14 0%, #0e0e1e 25%, #121228 50%, #0c1620 75%, #0a0a14 100%);
    --text-primary: rgba(255,255,255,0.88);
    --text-secondary: rgba(255,255,255,0.38);
    --text-muted: rgba(255,255,255,0.22);

    --glass-bg: rgba(255,255,255,0.025);
    --glass-bg-strong: rgba(255,255,255,0.05);
    --glass-bg-subtle: rgba(255,255,255,0.012);
    --glass-border: rgba(255,255,255,0.07);
    --glass-border-light: rgba(255,255,255,0.04);
    --glass-glow: rgba(255,255,255,0.02);
    --glass-inner-highlight: rgba(255,255,255,0.04);
    --glass-shadow: rgba(0,0,0,0.10);
    --glass-shadow-heavy: rgba(0,0,0,0.18);

    --cell-bg: rgba(255,255,255,0.018);
    --cell-border: rgba(255,255,255,0.05);
    --cell-hover-shadow: rgba(0,0,0,0.15), 0 0 16px rgba(100,140,255,0.05);

    --overlay-bg: rgba(0,0,0,0.25);

    --detail-bg: rgba(14,14,28,0.40);
    --detail-header-border: rgba(255,255,255,0.05);
    --detail-row-bg: rgba(255,255,255,0.025);
    --detail-row-border: rgba(255,255,255,0.04);

    --atom-bg: linear-gradient(135deg, rgba(10,10,20,0.3), rgba(14,10,24,0.3));

    --badge-bg: rgba(255,255,255,0.04);

    --toggle-bg: rgba(255,255,255,0.03);
    --toggle-border: rgba(255,255,255,0.06);

    --title-gradient: linear-gradient(135deg, #5eead4, #67e8f9, #93c5fd);
}

/* ============================================================
   RESET & BASE
   ============================================================ */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }

html, body {
    width: 100%; height: 100%;
    font-family: 'Nunito', 'Helvetica Neue', sans-serif;
    color: var(--text-primary);
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    transition: color var(--theme-speed) ease;
}
body {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    padding: 16px 24px;
    gap: 12px;
}
html::before {
    content: '';
    position: fixed;
    inset: 0;
    background: var(--bg-primary);
    z-index: -1;
    pointer-events: none;
}

/* ============================================================
   LAYOUT
   ============================================================ */
.app-container {
    display: flex;
    flex-direction: column;
    flex: 1;
    gap: 12px;
}

/* ============================================================
   HEADER
   ============================================================ */
.header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 20px;
    gap: 16px;
}
.controls-right {
    display: flex;
    gap: 8px;
    align-items: center;
}
.header-text { text-align: center; flex-shrink: 0; }
.header-text h1 {
    font-size: 2.4rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    background: var(--title-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}
/* ============================================================
   HEADER CONTROLS (shared)
   ============================================================ */
.theme-toggle,
.lang-toggle {
    position: relative;
    width: 44px; height: 44px;
    border-radius: 50%;
    border: 1px solid var(--glass-border);
    background: var(--toggle-bg);
    backdrop-filter: blur(6px);
    -webkit-backdrop-filter: blur(6px);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    color: var(--text-primary);
    transition: transform 0.3s cubic-bezier(0.34,1.56,0.64,1), box-shadow 0.3s ease, background var(--theme-speed) ease, border-color var(--theme-speed) ease;
    box-shadow: 0 1px 8px var(--glass-shadow), inset 0 1px 0 var(--glass-inner-highlight);
    overflow: hidden;
    z-index: 10;
}
.theme-toggle:hover,
.lang-toggle:hover {
    transform: scale(1.1);
    box-shadow: 0 2px 12px var(--glass-shadow-heavy), inset 0 1px 0 var(--glass-inner-highlight);
}
.theme-toggle:active,
.lang-toggle:active {
    transform: scale(0.95);
}

/* ============================================================
   HEADER LINKS (GitHub & Chem Lab)
   ============================================================ */
.lab-link,
.controls-right .github-link {
    width: 44px; height: 44px;
    border-radius: 50%;
    border: 1px solid var(--glass-border);
    background: var(--toggle-bg);
    backdrop-filter: blur(6px);
    -webkit-backdrop-filter: blur(6px);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-primary);
    text-decoration: none;
    transition: transform 0.3s cubic-bezier(0.34,1.56,0.64,1), box-shadow 0.3s ease, background var(--theme-speed) ease, border-color var(--theme-speed) ease;
    box-shadow: 0 1px 8px var(--glass-shadow), inset 0 1px 0 var(--glass-inner-highlight);
    overflow: hidden;
    z-index: 10;
}
.lab-link:hover,
.controls-right .github-link:hover {
    transform: scale(1.1);
    box-shadow: 0 2px 12px var(--glass-shadow-heavy), inset 0 1px 0 var(--glass-inner-highlight);
}
.lab-link:active,
.controls-right .github-link:active {
    transform: scale(0.95);
}
.lab-link svg,
.controls-right .github-link svg {
    flex-shrink: 0;
    transition: color var(--theme-speed) ease;
}

/* ============================================================
   LANGUAGE TOGGLE
   ============================================================ */
.lang-label {
    font-size: 0.82rem;
    font-weight: 700;
    letter-spacing: 0.02em;
    user-select: none;
}

/* ============================================================
   THEME TOGGLE
   ============================================================ */
.theme-toggle .icon-sun,
.theme-toggle .icon-moon {
    position: absolute;
    transition: opacity 0.4s cubic-bezier(0.34,1.56,0.64,1), transform 0.4s cubic-bezier(0.34,1.56,0.64,1);
    line-height: 1;
}
.theme-toggle .icon-sun  { opacity: 0; transform: rotate(-90deg) scale(0.5); }
.theme-toggle .icon-moon { opacity: 1; transform: rotate(0deg) scale(1); }
[data-theme="dark"] .theme-toggle .icon-sun  { opacity: 1; transform: rotate(0deg) scale(1); }
[data-theme="dark"] .theme-toggle .icon-moon { opacity: 0; transform: rotate(90deg) scale(0.5); }

/* ============================================================
   LEGEND
   ============================================================ */
.legend {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 8px;
    padding: 8px 16px;
    background: var(--glass-bg);
    backdrop-filter: blur(6px);
    -webkit-backdrop-filter: blur(6px);
    border: 1px solid var(--glass-border);
    border-radius: 12px;
    flex: 1;
    min-width: 0;
    box-shadow: 0 1px 10px var(--glass-shadow), inset 0 1px 0 var(--glass-inner-highlight);
    transition: background var(--theme-speed) ease, border-color var(--theme-speed) ease, box-shadow var(--theme-speed) ease;
}
.legend-item {
    display: flex;
    align-items: center;
    gap: 6px;
    font-size: 0.7rem;
    color: var(--text-secondary);
    font-weight: 500;
    transition: color var(--theme-speed) ease;
}
.legend-swatch {
    width: 14px; height: 14px;
    border-radius: 4px;
    border: 1px solid var(--glass-border-light);
}
.legend-label {
    white-space: nowrap;
}

/* ============================================================
   PERIODIC TABLE GRID
   ============================================================ */
.table-wrapper {
    overflow-x: auto;
    padding: 12px;
    background: var(--glass-bg-subtle);
    backdrop-filter: blur(6px);
    -webkit-backdrop-filter: blur(6px);
    border-radius: 20px;
    margin: 0 auto;
    max-width: 1400px;
    transition: background var(--theme-speed) ease, box-shadow var(--theme-speed) ease;
}

.periodic-table {
    display: grid;
    grid-template-columns: 40px repeat(18, minmax(60px, 1fr));
    grid-template-rows: repeat(11, auto);
    gap: 3px;
    min-width: 1140px;
}
.group-label {
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.6rem;
    font-weight: 600;
    color: var(--text-muted);
    padding: 2px 0;
    transition: color var(--theme-speed) ease;
}
.period-label {
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.6rem;
    font-weight: 600;
    color: var(--text-muted);
    padding: 0 2px;
    transition: color var(--theme-speed) ease;
}

/* ============================================================
   ELEMENT CELL
   ============================================================ */
.element {
    position: relative;
    aspect-ratio: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    border-radius: 10px;
    cursor: pointer;
    transition: transform 0.3s cubic-bezier(0.34, 1.56, 0.64, 1),
                box-shadow 0.3s ease,
                background var(--theme-speed) ease,
                border-color var(--theme-speed) ease;
    border: 1px solid var(--cell-border);
    overflow: hidden;
    user-select: none;
    padding: 4px 2px;
    background: var(--cell-bg);
    box-shadow: inset 0 1px 0 var(--glass-inner-highlight);
}
.element:hover {
    transform: translateY(-4px) scale(1.08);
    box-shadow: 0 4px 20px var(--glass-shadow-heavy), 0 0 16px var(--glass-glow), inset 0 1px 0 var(--glass-inner-highlight);
    z-index: 10;
    border-color: var(--glass-border);
    background: var(--cat, var(--glass-bg));
}
.element:active {
    transform: translateY(-2px) scale(1.04);
}
.element .atomic-number {
    font-size: 0.55rem;
    font-weight: 600;
    opacity: 0.65;
    position: absolute;
    top: 3px;
    left: 5px;
    color: var(--text-primary);
    transition: color var(--theme-speed) ease;
}
.element .symbol {
    font-size: 1.15rem;
    font-weight: 700;
    line-height: 1.1;
    letter-spacing: -0.01em;
    color: var(--text-primary);
    transition: color var(--theme-speed) ease;
}
.element .name {
    font-size: 0.42rem;
    font-weight: 500;
    opacity: 0.6;
    text-align: center;
    line-height: 1.15;
    max-width: 100%;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    color: var(--text-primary);
    transition: color var(--theme-speed) ease;
}
.element .mass {
    font-size: 0.42rem;
    font-weight: 400;
    opacity: 0.45;
    margin-top: 1px;
    color: var(--text-primary);
    transition: color var(--theme-speed) ease;
}

/* ============================================================
   ELEMENT CATEGORY COLORS — LIGHT
   ============================================================ */
.element[data-category="alkali-metal"]        { --cat: rgba(255,183,77,0.22); }
.element[data-category="alkaline-earth-metal"]{ --cat: rgba(255,224,130,0.22); }
.element[data-category="transition-metal"]    { --cat: rgba(255,171,145,0.20); }
.element[data-category="post-transition-metal"]{ --cat: rgba(159,213,203,0.20); }
.element[data-category="metalloid"]           { --cat: rgba(128,203,196,0.20); }
.element[data-category="nonmetal"]            { --cat: rgba(165,214,167,0.20); }
.element[data-category="halogen"]             { --cat: rgba(179,157,219,0.22); }
.element[data-category="noble-gas"]           { --cat: rgba(206,147,216,0.22); }
.element[data-category="lanthanide"]          { --cat: rgba(240,98,146,0.18); }
.element[data-category="actinide"]            { --cat: rgba(229,115,115,0.18); }
.element { background: var(--cat, var(--cell-bg)); }

/* Dark category overrides */
[data-theme="dark"] .element[data-category="alkali-metal"]        { --cat: rgba(255,183,77,0.14); }
[data-theme="dark"] .element[data-category="alkaline-earth-metal"]{ --cat: rgba(255,224,130,0.14); }
[data-theme="dark"] .element[data-category="transition-metal"]    { --cat: rgba(255,171,145,0.12); }
[data-theme="dark"] .element[data-category="post-transition-metal"]{ --cat: rgba(159,213,203,0.12); }
[data-theme="dark"] .element[data-category="metalloid"]           { --cat: rgba(128,203,196,0.12); }
[data-theme="dark"] .element[data-category="nonmetal"]            { --cat: rgba(165,214,167,0.12); }
[data-theme="dark"] .element[data-category="halogen"]             { --cat: rgba(179,157,219,0.12); }
[data-theme="dark"] .element[data-category="noble-gas"]           { --cat: rgba(206,147,216,0.12); }
[data-theme="dark"] .element[data-category="lanthanide"]          { --cat: rgba(240,98,146,0.10); }
[data-theme="dark"] .element[data-category="actinide"]            { --cat: rgba(229,115,115,0.10); }

/* ============================================================
   DETAIL PANEL OVERLAY
   ============================================================ */
.overlay {
    position: fixed;
    inset: 0;
    width: 100vw;
    height: 100vh;
    background: var(--overlay-bg);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    z-index: 1000;
    display: none;
    align-items: center;
    justify-content: center;
    transition: background var(--theme-speed) ease;
    border: none;
    padding: 0;
    margin: 0;
}
.overlay.active,
.overlay[open] {
    display: flex;
    animation: fadeIn 0.3s ease;
}

@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }

.detail-panel {
    width: 680px;
    max-width: 94vw;
    max-height: 92vh;
    margin: auto;
    background: var(--detail-bg);
    backdrop-filter: blur(10px) saturate(1.2);
    -webkit-backdrop-filter: blur(10px) saturate(1.2);
    border: 1px solid var(--glass-border);
    border-radius: 28px;
    box-shadow: 0 16px 48px var(--glass-shadow-heavy),
                0 0 1px var(--glass-shadow),
                inset 0 1px 0 var(--glass-inner-highlight);
    overflow: hidden;
    animation: panelIn 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
    display: flex;
    flex-direction: column;
    transition: background var(--theme-speed) ease, border-color var(--theme-speed) ease, box-shadow var(--theme-speed) ease;
}
@keyframes panelIn {
    from { opacity: 0; transform: scale(0.92) translateY(20px); }
    to   { opacity: 1; transform: scale(1) translateY(0); }
}

.detail-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 20px 24px 12px;
    border-bottom: 1px solid var(--detail-header-border);
    transition: border-color var(--theme-speed) ease;
}
.detail-header .element-badge {
    display: flex;
    align-items: center;
    gap: 16px;
}
.detail-header .badge-symbol {
    width: 64px; height: 64px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    font-weight: 800;
    border-radius: 16px;
    border: 1px solid var(--glass-border);
    background: var(--badge-bg);
    color: var(--text-primary);
    transition: background var(--theme-speed) ease, border-color var(--theme-speed) ease, color var(--theme-speed) ease;
    box-shadow: inset 0 1px 0 var(--glass-inner-highlight);
}
.detail-header .badge-info h2 {
    font-size: 1.4rem;
    font-weight: 700;
    color: var(--text-primary);
    transition: color var(--theme-speed) ease;
}
.detail-header .badge-info .subtitle {
    font-size: 0.8rem;
    color: var(--text-secondary);
    font-weight: 400;
    transition: color var(--theme-speed) ease;
}
.close-btn {
    width: 36px; height: 36px;
    border-radius: 50%;
    border: 1px solid var(--glass-border-light);
    background: var(--glass-bg);
    cursor: pointer;
    font-size: 1.1rem;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform 0.2s, background 0.2s, color 0.2s;
    box-shadow: inset 0 1px 0 var(--glass-inner-highlight);
}
.close-btn:hover {
    background: var(--glass-bg-strong);
    color: var(--text-primary);
}

.detail-body {
    display: flex;
    flex: 1;
    overflow: hidden;
}
.atom-viewer {
    width: 320px;
    min-height: 300px;
    position: relative;
    background: var(--atom-bg);
    border-right: 1px solid var(--detail-header-border);
    transition: background var(--theme-speed) ease, border-color var(--theme-speed) ease;
}
.atom-viewer canvas { display: block; }
.atom-label {
    position: absolute;
    bottom: 12px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 0.7rem;
    color: var(--text-muted);
    font-weight: 500;
    background: var(--glass-bg);
    padding: 4px 12px;
    border-radius: 20px;
    backdrop-filter: blur(4px);
    border: 1px solid var(--glass-border-light);
    transition: background var(--theme-speed) ease, border-color var(--theme-speed) ease, color var(--theme-speed) ease;
}

/* ============================================================
   MODE TOGGLE (Bohr / Orbital)
   ============================================================ */
.mode-toggle {
    position: absolute;
    top: 10px;
    right: 10px;
    display: flex;
    border-radius: 20px;
    border: 1px solid var(--glass-border-light);
    background: var(--glass-bg);
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
    overflow: hidden;
    z-index: 5;
    box-shadow: 0 1px 6px var(--glass-shadow), inset 0 1px 0 var(--glass-inner-highlight);
    transition: background var(--theme-speed) ease, border-color var(--theme-speed) ease;
}
.mode-btn {
    padding: 4px 14px;
    font-size: 0.68rem;
    font-weight: 600;
    letter-spacing: 0.02em;
    border: none;
    background: transparent;
    color: var(--text-muted);
    cursor: pointer;
    transition: all 0.25s ease;
    user-select: none;
}
.mode-btn:hover {
    color: var(--text-secondary);
}
.mode-btn.active {
    background: var(--glass-bg-strong);
    color: var(--text-primary);
    box-shadow: inset 0 1px 0 var(--glass-inner-highlight);
}

.detail-info {
    flex: 1;
    padding: 20px 24px;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 14px;
}
.info-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 8px 12px;
    background: var(--detail-row-bg);
    border-radius: 10px;
    border: 1px solid var(--detail-row-border);
    transition: background var(--theme-speed) ease, border-color var(--theme-speed) ease;
    box-shadow: inset 0 1px 0 var(--glass-inner-highlight);
}
.info-row .label {
    font-size: 0.72rem;
    color: var(--text-secondary);
    font-weight: 500;
    transition: color var(--theme-speed) ease;
}
.info-row .value {
    font-size: 0.82rem;
    font-weight: 600;
    color: var(--text-primary);
    transition: color var(--theme-speed) ease;
}
.electron-config {
    padding: 12px;
    background: var(--detail-row-bg);
    border-radius: 10px;
    border: 1px solid var(--detail-row-border);
    transition: background var(--theme-speed) ease, border-color var(--theme-speed) ease;
    box-shadow: inset 0 1px 0 var(--glass-inner-highlight);
}
.electron-config .label {
    font-size: 0.72rem;
    color: var(--text-secondary);
    font-weight: 500;
    margin-bottom: 4px;
    transition: color var(--theme-speed) ease;
}
.electron-config .value {
    font-size: 0.78rem;
    font-weight: 600;
    color: var(--text-primary);
    font-family: 'SF Mono', 'Fira Code', monospace;
    transition: color var(--theme-speed) ease;
}
.shells-display {
    display: flex;
    gap: 6px;
    flex-wrap: wrap;
}
.shell-chip {
    padding: 4px 10px;
    background: var(--glass-bg);
    border-radius: 20px;
    border: 1px solid var(--glass-border-light);
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--text-secondary);
    transition: background var(--theme-speed) ease, border-color var(--theme-speed) ease, color var(--theme-speed) ease;
}


/* ============================================================
   SCROLLBAR (theme-aware)
   ============================================================ */
.detail-info::-webkit-scrollbar { width: 6px; }
.detail-info::-webkit-scrollbar-track { background: transparent; }
.detail-info::-webkit-scrollbar-thumb {
    background: var(--glass-border-light);
    border-radius: 3px;
}

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 768px) {
    body { padding: 8px 12px; gap: 8px; }
    .app-container { gap: 8px; }
    .header { flex-wrap: wrap; gap: 8px; padding: 8px 12px; }
    .header-text h1 { font-size: 1.4rem; }
    .legend { order: 3; width: 100%; flex-basis: 100%; }
    .detail-body { flex-direction: column; }
    .atom-viewer { width: 100%; min-height: 250px; border-right: none; border-bottom: 1px solid var(--detail-header-border); }
    .detail-panel { border-radius: 20px; }
}