/* ============================================================
   CSS Custom Properties (Theme Variables)
   ============================================================ */
:root,
[data-theme="dark"] {
    --bg-page:           #1a1d23;
    --bg-header:         #12151a;
    --bg-footer:         #12151a;
    --bg-panel:          #21252b;
    --bg-panel-hd:       #2c313a;
    --bg-input:          #1e2229;
    --bg-btn-primary:    #4a9eff;
    --bg-btn-primary-hv: #3a8eef;
    --bg-btn-secondary:  #3d424d;
    --bg-btn-secondary-hv: #4d535f;
    --bg-btn-success:    #4caf7d;
    --bg-btn-success-hv: #3c9f6d;
    --bg-badge:          #2c313a;
    --text-primary:      #abb2bf;
    --text-heading:      #e6e6e6;
    --text-muted:        #636d83;
    --text-on-primary:   #ffffff;
    --text-link:         #4a9eff;
    --brand-color:       #4a9eff;
    --border-color:      #3d424d;
    --border-input:      #3d424d;
    --border-input-focus:#4a9eff;
    --scrollbar-thumb:   #3d424d;
    --scrollbar-track:   #1a1d23;
    --status-success-bg: rgba(76,175,125,0.15);
    --status-success-bdr:#4caf7d;
    --status-error-bg:   rgba(224,108,117,0.15);
    --status-error-bdr:  #e06c75;
    --status-info-bg:    rgba(74,158,255,0.12);
    --status-info-bdr:   #4a9eff;
    --shadow-panel:      0 2px 12px rgba(0,0,0,0.35);
    --output-bg:         #1e2229;
    --output-text:       #61afef;
}

[data-theme="light"] {
    --bg-page:           #f0f2f5;
    --bg-header:         #ffffff;
    --bg-footer:         #ffffff;
    --bg-panel:          #ffffff;
    --bg-panel-hd:       #f0f2f5;
    --bg-input:          #ffffff;
    --bg-btn-primary:    #2979ff;
    --bg-btn-primary-hv: #1a68ee;
    --bg-btn-secondary:  #e0e3ea;
    --bg-btn-secondary-hv: #d0d4de;
    --bg-btn-success:    #2e7d52;
    --bg-btn-success-hv: #246642;
    --bg-badge:          #e8ecf2;
    --text-primary:      #383a42;
    --text-heading:      #181a1f;
    --text-muted:        #888ea0;
    --text-on-primary:   #ffffff;
    --text-link:         #2979ff;
    --brand-color:       #2979ff;
    --border-color:      #d4d8e1;
    --border-input:      #c8cdd8;
    --border-input-focus:#2979ff;
    --scrollbar-thumb:   #c0c4cc;
    --scrollbar-track:   #f0f2f5;
    --status-success-bg: rgba(46,125,82,0.08);
    --status-success-bdr:#2e7d52;
    --status-error-bg:   rgba(198,40,40,0.08);
    --status-error-bdr:  #c62828;
    --status-info-bg:    rgba(41,121,255,0.08);
    --status-info-bdr:   #2979ff;
    --shadow-panel:      0 2px 12px rgba(0,0,0,0.08);
    --output-bg:         #f8f9fb;
    --output-text:       #1a5cb8;
}

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

html { font-size: 14px; scroll-behavior: smooth; }

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background: var(--bg-page);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    transition: background 0.2s, color 0.2s;
}

a {
    color: var(--text-link);
    text-decoration: none;
}
a:hover { text-decoration: underline; }

h1, h2, h3, h4 {
    color: var(--text-heading);
    line-height: 1.3;
}

/* Scrollbar */
::-webkit-scrollbar { width: 8px; height: 8px; }
::-webkit-scrollbar-track { background: var(--scrollbar-track); }
::-webkit-scrollbar-thumb { background: var(--scrollbar-thumb); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: var(--brand-color); }

/* ============================================================
   Header
   ============================================================ */
.app-header {
    background: var(--bg-header);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 1px 4px rgba(0,0,0,0.2);
}

.header-inner {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.25rem;
    height: 52px;
    display: flex;
    align-items: center;
    gap: 1rem;
}

.app-brand {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-heading);
    text-decoration: none;
    white-space: nowrap;
    flex-shrink: 0;
}
.app-brand:hover { text-decoration: none; color: var(--brand-color); }

.brand-icon {
    font-size: 1.3rem;
    line-height: 1;
    color: var(--brand-color);
}

/* Nav */
.app-nav { margin-left: auto; }

.nav-list {
    list-style: none;
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

.nav-link {
    display: block;
    padding: 0.35rem 0.7rem;
    border-radius: 5px;
    color: var(--text-primary);
    font-size: 0.875rem;
    font-weight: 500;
    transition: color 0.15s, background 0.15s;
    text-decoration: none;
}
.nav-link:hover { color: var(--brand-color); background: rgba(74,158,255,0.08); text-decoration: none; }
.nav-link.active { color: var(--brand-color); }

/* Theme Toggle */
.theme-toggle-btn {
    background: var(--bg-btn-secondary);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    width: 34px;
    height: 34px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1rem;
    flex-shrink: 0;
    transition: background 0.15s, border-color 0.15s;
}
.theme-toggle-btn:hover { background: var(--bg-btn-secondary-hv); border-color: var(--brand-color); }

/* Hamburger */
.nav-hamburger {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 6px;
    margin-left: auto;
    border-radius: 5px;
}
.nav-hamburger span {
    display: block;
    width: 20px;
    height: 2px;
    background: var(--text-primary);
    border-radius: 2px;
    transition: transform 0.2s, opacity 0.2s;
}

/* ============================================================
   Footer
   ============================================================ */
.app-footer {
    background: var(--bg-footer);
    border-top: 1px solid var(--border-color);
    padding: 0.9rem 1.25rem;
    margin-top: auto;
    font-size: 0.8rem;
    color: var(--text-muted);
}
.footer-inner {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    flex-wrap: wrap;
}
.footer-links { display: flex; gap: 1rem; }
.footer-links a { color: var(--text-muted); }
.footer-links a:hover { color: var(--brand-color); }
.app-footer a { color: var(--text-muted); }
.app-footer a:hover { color: var(--brand-color); text-decoration: none; }

/* ============================================================
   Main / Page Layout
   ============================================================ */
main { flex: 1; }

.page-hero {
    background: var(--bg-panel);
    border-bottom: 1px solid var(--border-color);
    padding: 1.5rem 1.25rem 1.25rem;
    text-align: center;
}

.page-hero h1 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-heading);
    margin-bottom: 0.35rem;
}

.page-hero p {
    color: var(--text-muted);
    font-size: 0.9rem;
}

.page-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1.5rem 1.25rem 2rem;
}

/* ============================================================
   Converter Grid
   ============================================================ */
.converter-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.25rem;
    align-items: start;
}

/* ============================================================
   Card
   ============================================================ */
.card {
    background: var(--bg-panel);
    border: 1px solid var(--border-color);
    border-radius: 10px;
    box-shadow: var(--shadow-panel);
    overflow: hidden;
}

.card-header {
    background: var(--bg-panel-hd);
    border-bottom: 1px solid var(--border-color);
    padding: 0.75rem 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.card-header h2 {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-heading);
    flex: 1;
}

.card-icon {
    font-size: 1rem;
    color: var(--brand-color);
}

.card-body {
    padding: 1.1rem 1rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

/* ============================================================
   Form Controls
   ============================================================ */
.field-group {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.field-label {
    font-size: 0.78rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.04em;
}

.field-input {
    width: 100%;
    background: var(--bg-input);
    border: 1px solid var(--border-input);
    border-radius: 6px;
    padding: 0.55rem 0.75rem;
    font-size: 0.95rem;
    font-family: "Fira Code", "Cascadia Code", "Consolas", "Monaco", monospace;
    color: var(--text-heading);
    transition: border-color 0.15s, box-shadow 0.15s;
    appearance: none;
    -webkit-appearance: none;
}

.field-input:focus {
    outline: none;
    border-color: var(--border-input-focus);
    box-shadow: 0 0 0 3px rgba(74,158,255,0.18);
}

[data-theme="light"] .field-input:focus {
    box-shadow: 0 0 0 3px rgba(41,121,255,0.14);
}

.field-input[type="date"],
.field-input[type="time"] {
    cursor: text;
    color-scheme: dark;
}

[data-theme="light"] .field-input[type="date"],
[data-theme="light"] .field-input[type="time"] {
    color-scheme: light;
}

.field-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0.75rem;
}

/* Toggle Group */
.toggle-group {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.toggle-row {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.toggle-label {
    font-size: 0.78rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.04em;
    min-width: 60px;
}

.btn-group {
    display: flex;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    overflow: hidden;
}

.btn-group-item {
    padding: 0.3rem 0.7rem;
    font-size: 0.8rem;
    font-weight: 500;
    background: var(--bg-btn-secondary);
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    transition: background 0.15s, color 0.15s;
    border-right: 1px solid var(--border-color);
}
.btn-group-item:last-child { border-right: none; }
.btn-group-item:hover { background: var(--bg-btn-secondary-hv); color: var(--text-heading); }
.btn-group-item.active {
    background: var(--brand-color);
    color: #fff;
}

/* ============================================================
   Buttons
   ============================================================ */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    padding: 0.5rem 1rem;
    border: none;
    border-radius: 6px;
    font-size: 0.875rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.15s, transform 0.1s, opacity 0.15s;
    white-space: nowrap;
    text-decoration: none;
}
.btn:active { transform: scale(0.97); }
.btn:disabled { opacity: 0.5; cursor: not-allowed; transform: none; }

.btn-primary {
    background: var(--bg-btn-primary);
    color: var(--text-on-primary);
}
.btn-primary:hover { background: var(--bg-btn-primary-hv); }

.btn-secondary {
    background: var(--bg-btn-secondary);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}
.btn-secondary:hover { background: var(--bg-btn-secondary-hv); color: var(--text-heading); }

.btn-success {
    background: var(--bg-btn-success);
    color: #fff;
}
.btn-success:hover { background: var(--bg-btn-success-hv); }

.btn-sm {
    padding: 0.3rem 0.65rem;
    font-size: 0.8rem;
}

.btn-icon { font-size: 0.85rem; }

.action-row {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

/* ============================================================
   Output Display
   ============================================================ */
.output-section {
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
}

.output-block {
    background: var(--output-bg);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    padding: 0.75rem 0.9rem;
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
    min-height: 52px;
}

.output-block-content {
    flex: 1;
    min-width: 0;
}

.output-block-label {
    font-size: 0.72rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.2rem;
}

.output-block-value {
    font-family: "Fira Code", "Cascadia Code", "Consolas", "Monaco", monospace;
    font-size: 1rem;
    font-weight: 600;
    color: var(--output-text);
    word-break: break-all;
}

.output-block-value.empty {
    color: var(--text-muted);
    font-weight: 400;
    font-size: 0.85rem;
    font-family: inherit;
}

.copy-btn {
    background: none;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    color: var(--text-muted);
    cursor: pointer;
    padding: 0.3rem 0.45rem;
    font-size: 0.85rem;
    flex-shrink: 0;
    transition: background 0.15s, color 0.15s, border-color 0.15s;
}
.copy-btn:hover {
    background: var(--bg-btn-secondary);
    color: var(--brand-color);
    border-color: var(--brand-color);
}
.copy-btn.copied {
    color: var(--bg-btn-success);
    border-color: var(--bg-btn-success);
}

/* ============================================================
   Status / Alert
   ============================================================ */
.status-bar {
    border-radius: 6px;
    padding: 0.55rem 0.8rem;
    font-size: 0.85rem;
    display: none;
    align-items: center;
    gap: 0.5rem;
}
.status-bar.visible { display: flex; }
.status-bar.success { background: var(--status-success-bg); border: 1px solid var(--status-success-bdr); color: var(--status-success-bdr); }
.status-bar.error   { background: var(--status-error-bg);   border: 1px solid var(--status-error-bdr);   color: var(--status-error-bdr); }
.status-bar.info    { background: var(--status-info-bg);    border: 1px solid var(--status-info-bdr);    color: var(--status-info-bdr); }

/* ============================================================
   Info / Tip Callout
   ============================================================ */
.callout {
    border-radius: 7px;
    padding: 0.75rem 1rem;
    font-size: 0.83rem;
    line-height: 1.5;
    border-left: 3px solid var(--brand-color);
    background: var(--status-info-bg);
    color: var(--text-muted);
}
.callout strong { color: var(--text-primary); }

/* ============================================================
   Static / Content Pages
   ============================================================ */
.content-page {
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem 1.25rem 3rem;
}

.content-page h1 {
    font-size: 1.6rem;
    margin-bottom: 0.4rem;
}

.content-page .page-meta {
    color: var(--text-muted);
    font-size: 0.85rem;
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--border-color);
}

.content-page h2 {
    font-size: 1.1rem;
    margin-top: 1.75rem;
    margin-bottom: 0.6rem;
    padding-bottom: 0.35rem;
    border-bottom: 1px solid var(--border-color);
    color: var(--brand-color);
}

.content-page p {
    margin-bottom: 0.9rem;
    line-height: 1.75;
}

.content-page ul {
    margin-left: 1.5rem;
    margin-bottom: 0.9rem;
    line-height: 1.75;
}

/* ============================================================
   Error Page
   ============================================================ */
.error-page {
    max-width: 600px;
    margin: 4rem auto;
    padding: 2rem 1.25rem;
    text-align: center;
}
.error-code {
    font-size: 4rem;
    font-weight: 900;
    color: var(--brand-color);
    line-height: 1;
    margin-bottom: 0.5rem;
    font-family: "Fira Code", monospace;
}
.error-page h1 { font-size: 1.4rem; margin-bottom: 0.75rem; }
.error-page p { color: var(--text-muted); margin-bottom: 1rem; }
.request-id {
    font-family: monospace;
    font-size: 0.78rem;
    color: var(--text-muted);
    background: var(--bg-panel-hd);
    padding: 0.3rem 0.6rem;
    border-radius: 4px;
    display: inline-block;
    margin-bottom: 1.5rem;
}

/* ============================================================
   Responsive
   ============================================================ */
@media (max-width: 768px) {
    .converter-grid {
        grid-template-columns: 1fr;
    }

    .app-nav {
        display: none;
        position: absolute;
        top: 52px;
        left: 0;
        right: 0;
        background: var(--bg-header);
        border-bottom: 1px solid var(--border-color);
        padding: 0.5rem 0;
        z-index: 99;
    }
    .app-nav.open { display: block; }
    .nav-list { flex-direction: column; gap: 0; }
    .nav-link { padding: 0.6rem 1.25rem; border-radius: 0; }

    .nav-hamburger { display: flex; }
    .app-header { position: relative; }

    .header-inner { flex-wrap: wrap; }

    .field-row { grid-template-columns: 1fr; }

    .page-hero h1 { font-size: 1.2rem; }
}

@media (max-width: 480px) {
    .footer-inner { flex-direction: column; text-align: center; }
}