/* ═══════════════════════════════════════════════════════════════════════════
   PDF Merger Pro — app.css
   Dark mode premium · Glassmorphism · Micro-animaciones
   ═══════════════════════════════════════════════════════════════════════════ */

/* ── Google Fonts fallback ────────────────────────────────────────────────── */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&display=swap');

/* ── Variables de diseño ──────────────────────────────────────────────────── */
:root {
    /* Paleta dark */
    --bg-base:        #0d1117;
    --bg-card:        #161b22;
    --bg-card-hover:  #1c2330;
    --bg-input:       #0d1117;
    --border:         rgba(255,255,255,0.08);
    --border-hover:   rgba(255,255,255,0.18);

    /* Acentos */
    --accent:         #e74c3c;
    --accent-light:   #ff6b6b;
    --accent-glow:    rgba(231,76,60,0.25);
    --accent-2:       #f39c12;

    /* Gradiente principal */
    --grad-primary:   linear-gradient(135deg, #e74c3c 0%, #f39c12 100%);
    --grad-hero:      linear-gradient(160deg, #0d1117 0%, #161b22 60%, #1a0f0f 100%);

    /* Textos */
    --text-primary:   #e6edf3;
    --text-secondary: #8b949e;
    --text-muted:     #484f58;

    /* Éxito / peligro */
    --success:        #2ea043;
    --success-light:  #3fb950;
    --danger:         #f85149;

    /* Radio y sombras */
    --radius-sm:   8px;
    --radius-md:  14px;
    --radius-lg:  20px;
    --radius-xl:  28px;

    --shadow-card: 0 4px 24px rgba(0,0,0,0.4);
    --shadow-glow: 0 0 40px var(--accent-glow);
    --shadow-btn:  0 4px 20px rgba(231,76,60,0.4);

    /* Transiciones */
    --ease: cubic-bezier(0.4, 0, 0.2, 1);
    --dur:  0.22s;
}

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

html { scroll-behavior: smooth; }

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    background-color: var(--bg-base);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    overflow-x: hidden;
}

/* ── Scrollbar custom ─────────────────────────────────────────────────────── */
::-webkit-scrollbar { width: 8px; }
::-webkit-scrollbar-track { background: var(--bg-base); }
::-webkit-scrollbar-thumb { background: var(--border-hover); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-muted); }

/* ═══════════════════════════════════════════════════════ NAVBAR ════════════ */
.navbar {
    background: rgba(13,17,23,0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border);
    padding-top: 0.75rem;
    padding-bottom: 0.75rem;
    z-index: 1000;
}

.brand-icon {
    width: 36px; height: 36px;
    background: var(--grad-primary);
    border-radius: var(--radius-sm);
    display: flex; align-items: center; justify-content: center;
    font-size: 1.1rem;
    color: #fff;
    box-shadow: 0 0 14px var(--accent-glow);
    transition: transform var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}
.brand-icon:hover { transform: scale(1.08) rotate(-4deg); box-shadow: 0 0 22px var(--accent-glow); }

.brand-name {
    font-size: 1.1rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    color: var(--text-primary);
}

.badge-version {
    font-size: 0.68rem;
    font-weight: 600;
    color: var(--text-muted);
    background: var(--bg-card);
    border: 1px solid var(--border);
    padding: 3px 8px;
    border-radius: 20px;
    letter-spacing: 0.04em;
}

.nav-link-custom {
    font-size: 0.85rem;
    color: var(--text-secondary);
    text-decoration: none;
    transition: color var(--dur) var(--ease);
    display: flex; align-items: center;
}
.nav-link-custom:hover { color: var(--text-primary); }

/* ═══════════════════════════════════════════════════════ HERO ══════════════ */
.hero-section {
    background: var(--grad-hero);
    padding: 5rem 1rem 3.5rem;
    position: relative;
    overflow: hidden;
}

/* Fondo de rejilla sutil */
.hero-section::before {
    content: '';
    position: absolute;
    inset: 0;
    background-image:
        linear-gradient(rgba(231,76,60,0.04) 1px, transparent 1px),
        linear-gradient(90deg, rgba(231,76,60,0.04) 1px, transparent 1px);
    background-size: 40px 40px;
    pointer-events: none;
}

/* Glow orbs */
.hero-section::after {
    content: '';
    position: absolute;
    top: -80px; left: 50%;
    transform: translateX(-50%);
    width: 600px; height: 400px;
    background: radial-gradient(ellipse, rgba(231,76,60,0.12) 0%, transparent 70%);
    pointer-events: none;
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    font-size: 0.78rem;
    font-weight: 500;
    color: var(--accent-light);
    background: rgba(231,76,60,0.1);
    border: 1px solid rgba(231,76,60,0.25);
    padding: 5px 14px;
    border-radius: 20px;
    letter-spacing: 0.01em;
    position: relative;
    z-index: 1;
}

.hero-title {
    font-size: clamp(2.4rem, 6vw, 4rem);
    font-weight: 800;
    letter-spacing: -0.04em;
    line-height: 1.1;
    margin: 1rem 0 1rem;
    position: relative;
    z-index: 1;
}

.gradient-text {
    background: var(--grad-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.05rem;
    color: var(--text-secondary);
    max-width: 520px;
    margin: 0 auto;
    font-weight: 400;
    position: relative;
    z-index: 1;
}

.hero-stats { position: relative; z-index: 1; }

.stat-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2px;
}
.stat-num {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--text-primary);
}
.stat-label {
    font-size: 0.72rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}
.stat-divider {
    width: 1px;
    height: 32px;
    background: var(--border);
}

/* ═══════════════════════════════════════════════════ APP CARDS ═════════════ */
.container { max-width: 780px; }

.app-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-card);
    transition: border-color var(--dur) var(--ease);
}
.app-card:hover { border-color: var(--border-hover); }

.card-header-custom {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 1rem 1.25rem;
    border-bottom: 1px solid var(--border);
    background: rgba(255,255,255,0.02);
}
.card-title-custom {
    font-weight: 600;
    font-size: 0.95rem;
    color: var(--text-primary);
}
.text-accent { color: var(--accent-light) !important; }

.file-count-badge {
    background: var(--accent);
    color: #fff;
    font-size: 0.72rem;
    padding: 2px 7px;
    border-radius: 10px;
    font-weight: 700;
    min-width: 22px;
    text-align: center;
}

/* ═══════════════════════════════════════════════ DROP ZONE ═════════════════ */
.drop-zone {
    position: relative;
    min-height: 220px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: background var(--dur) var(--ease);
    padding: 2rem;
}

.drop-zone-content {
    text-align: center;
    pointer-events: none;
    transition: opacity var(--dur) var(--ease);
}

.drop-icon-wrap {
    width: 72px; height: 72px;
    background: rgba(231,76,60,0.1);
    border: 2px solid rgba(231,76,60,0.2);
    border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    margin: 0 auto;
    transition: transform var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}

.drop-icon {
    font-size: 2rem;
    color: var(--accent-light);
    display: block;
}

.drop-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 4px;
}
.drop-subtitle {
    font-size: 0.88rem;
    color: var(--text-secondary);
    margin-bottom: 0;
}

.format-badge {
    display: inline-block;
    background: rgba(231,76,60,0.15);
    color: var(--accent-light);
    border: 1px solid rgba(231,76,60,0.3);
    font-size: 0.72rem;
    font-weight: 700;
    padding: 2px 10px;
    border-radius: 4px;
    letter-spacing: 0.08em;
    margin-right: 6px;
}
.drop-limit {
    font-size: 0.75rem;
    color: var(--text-muted);
}

/* Estado hover de la drop zone */
.drop-zone:hover .drop-icon-wrap,
.drop-zone:focus .drop-icon-wrap {
    transform: translateY(-4px) scale(1.05);
    box-shadow: 0 8px 24px var(--accent-glow);
}

/* Estado drag-over */
.drop-zone.drag-over {
    background: rgba(231,76,60,0.06);
    border: 2px dashed var(--accent);
}
.drop-zone.drag-over .drop-zone-content { opacity: 0.3; }
.drop-zone.drag-over .drop-overlay { opacity: 1; pointer-events: none; }

.drop-overlay {
    position: absolute;
    inset: 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 12px;
    opacity: 0;
    transition: opacity var(--dur) var(--ease);
    color: var(--accent-light);
    font-size: 0.95rem;
    font-weight: 600;
    pointer-events: none;
}
.drop-overlay i { font-size: 3rem; animation: bounce 0.6s infinite alternate; }

@keyframes bounce {
    from { transform: translateY(0); }
    to   { transform: translateY(-10px); }
}

/* ═════════════════════════════════════════ PROGRESS BAR ════════════════════ */
.upload-progress-bar-wrap {
    padding: 0 4px;
}
.progress-label {
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--text-secondary);
}
.progress-pct {
    font-size: 0.85rem;
    font-weight: 700;
    color: var(--accent-light);
}
.progress { background: var(--bg-card); border: 1px solid var(--border); }
.progress-bar { background: var(--grad-primary); }

/* ══════════════════════════════════════════ FILE LIST ══════════════════════ */
.list-hint {
    font-size: 0.78rem;
    color: var(--text-muted);
    padding: 8px 1.25rem;
    border-bottom: 1px solid var(--border);
    background: rgba(255,255,255,0.015);
}

.file-list {
    list-style: none;
    padding: 0.5rem;
    max-height: 380px;
    overflow-y: auto;
}

/* Item de la lista */
.file-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 12px;
    border-radius: var(--radius-sm);
    border: 1px solid transparent;
    cursor: grab;
    transition: background var(--dur) var(--ease),
                border-color var(--dur) var(--ease),
                transform var(--dur) var(--ease);
    user-select: none;
    position: relative;
}
.file-item:hover {
    background: var(--bg-card-hover);
    border-color: var(--border);
}
.file-item:active { cursor: grabbing; }

/* Sortable ghost */
.file-item.sortable-ghost {
    opacity: 0.4;
    background: rgba(231,76,60,0.05);
    border: 1px dashed var(--accent);
}

/* Sortable chosen */
.file-item.sortable-chosen {
    transform: rotate(1.5deg) scale(1.02);
    box-shadow: 0 8px 24px rgba(0,0,0,0.5);
    z-index: 10;
    background: var(--bg-card-hover);
    border-color: var(--accent);
}

.file-drag-handle {
    color: var(--text-muted);
    font-size: 1.1rem;
    flex-shrink: 0;
    cursor: grab;
    padding: 2px;
    transition: color var(--dur) var(--ease);
}
.file-item:hover .file-drag-handle { color: var(--text-secondary); }

.file-order {
    font-size: 0.72rem;
    font-weight: 700;
    color: var(--text-muted);
    min-width: 20px;
    text-align: center;
    flex-shrink: 0;
}

.file-icon {
    font-size: 1.5rem;
    color: var(--accent);
    flex-shrink: 0;
}

.file-info { flex: 1; min-width: 0; }
.file-name {
    font-size: 0.88rem;
    font-weight: 500;
    color: var(--text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}
.file-size {
    font-size: 0.74rem;
    color: var(--text-muted);
    margin-top: 1px;
}

/* Estado de carga del archivo */
.file-status {
    flex-shrink: 0;
    display: flex;
    align-items: center;
    gap: 6px;
}
.file-status .uploading {
    width: 60px;
    height: 4px;
    background: var(--border);
    border-radius: 2px;
    overflow: hidden;
}
.file-status .uploading::after {
    content: '';
    display: block;
    height: 100%;
    width: 40%;
    background: var(--grad-primary);
    border-radius: 2px;
    animation: upload-shimmer 1s infinite;
}
@keyframes upload-shimmer {
    0%   { transform: translateX(-150%); }
    100% { transform: translateX(350%); }
}

.file-status .done { color: var(--success-light); font-size: 1rem; }
.file-status .error { color: var(--danger); font-size: 0.75rem; font-weight: 500; }

.file-delete-btn {
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 0.95rem;
    padding: 4px 6px;
    border-radius: 4px;
    cursor: pointer;
    transition: color var(--dur) var(--ease), background var(--dur) var(--ease);
    flex-shrink: 0;
    opacity: 0;
}
.file-item:hover .file-delete-btn { opacity: 1; }
.file-delete-btn:hover { color: var(--danger); background: rgba(248,81,73,0.1); }

/* Separador entre items */
.file-item + .file-item { margin-top: 2px; }

/* ══════════════════════════════════════════ BOTONES ICONO ══════════════════ */
.btn-icon-sm {
    background: var(--bg-base);
    border: 1px solid var(--border);
    color: var(--text-secondary);
    width: 32px; height: 32px;
    border-radius: var(--radius-sm);
    display: flex; align-items: center; justify-content: center;
    font-size: 0.9rem;
    cursor: pointer;
    transition: all var(--dur) var(--ease);
}
.btn-icon-sm:hover {
    background: var(--bg-card-hover);
    border-color: var(--border-hover);
    color: var(--text-primary);
}
.btn-icon-sm.danger:hover {
    color: var(--danger);
    border-color: var(--danger);
    background: rgba(248,81,73,0.08);
}

/* ══════════════════════════════════════════ MERGE CARD ══════════════════════ */
.merge-card .card-header-custom { display: flex; }
.merge-options { padding: 1.25rem; }

.option-group { margin-bottom: 0; }

.option-label {
    display: block;
    font-size: 0.83rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: 8px;
}

.input-group-custom {
    display: flex;
    align-items: center;
    background: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    overflow: hidden;
    transition: border-color var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}
.input-group-custom:focus-within {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.input-custom {
    flex: 1;
    background: transparent;
    border: none;
    outline: none;
    color: var(--text-primary);
    font-size: 0.9rem;
    padding: 10px 14px;
    font-family: inherit;
}
.input-custom::placeholder { color: var(--text-muted); }

.input-suffix {
    padding: 10px 12px;
    font-size: 0.85rem;
    color: var(--text-muted);
    border-left: 1px solid var(--border);
    background: rgba(255,255,255,0.02);
    font-weight: 500;
}

/* Botón principal UNIR ─────────────────────────────────────────────────────── */
.btn-merge {
    display: flex;
    align-items: center;
    justify-content: center;
    width: calc(100% - 2.5rem);
    margin: 0 1.25rem 1.25rem;
    padding: 14px 24px;
    background: var(--grad-primary);
    color: #fff;
    border: none;
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-weight: 700;
    font-family: inherit;
    cursor: pointer;
    box-shadow: var(--shadow-btn);
    transition: opacity var(--dur) var(--ease),
                transform var(--dur) var(--ease),
                box-shadow var(--dur) var(--ease);
    letter-spacing: -0.01em;
}
.btn-merge:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 8px 28px rgba(231,76,60,0.5);
}
.btn-merge:active:not(:disabled) { transform: translateY(0); }
.btn-merge:disabled { opacity: 0.55; cursor: not-allowed; transform: none; }

.merge-btn-content,
.merge-spinner {
    display: flex;
    align-items: center;
}

.merge-info {
    font-size: 0.76rem;
    color: var(--text-muted);
    text-align: center;
    padding: 0 1.25rem 1rem;
}

/* ══════════════════════════════════════════ RESULT CARD ════════════════════ */
.result-card {
    border-color: rgba(46,160,67,0.3);
    background: linear-gradient(135deg, rgba(46,160,67,0.05) 0%, var(--bg-card) 100%);
}

.result-success {
    padding: 2.5rem 1.5rem;
    text-align: center;
}

.result-icon {
    width: 80px; height: 80px;
    background: rgba(46,160,67,0.12);
    border: 2px solid rgba(63,185,80,0.3);
    border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    margin: 0 auto 1.25rem;
    font-size: 2.2rem;
    color: var(--success-light);
    animation: pop-in 0.4s var(--ease);
}

@keyframes pop-in {
    0%   { transform: scale(0.5); opacity: 0; }
    70%  { transform: scale(1.1); }
    100% { transform: scale(1); opacity: 1; }
}

.result-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 0.75rem;
}

.result-meta {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    display: flex;
    justify-content: center;
    gap: 12px;
    flex-wrap: wrap;
}
.result-meta span {
    display: flex;
    align-items: center;
    gap: 4px;
}

.btn-download {
    display: inline-flex;
    align-items: center;
    background: var(--grad-primary);
    color: #fff;
    border: none;
    padding: 12px 28px;
    border-radius: var(--radius-md);
    font-size: 0.95rem;
    font-weight: 700;
    font-family: inherit;
    cursor: pointer;
    text-decoration: none;
    box-shadow: var(--shadow-btn);
    transition: transform var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
    margin-bottom: 0.75rem;
}
.btn-download:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 28px rgba(231,76,60,0.5);
    color: #fff;
}

.btn-new {
    display: inline-flex;
    align-items: center;
    background: transparent;
    color: var(--text-secondary);
    border: 1px solid var(--border);
    padding: 10px 22px;
    border-radius: var(--radius-md);
    font-size: 0.88rem;
    font-weight: 500;
    font-family: inherit;
    cursor: pointer;
    transition: all var(--dur) var(--ease);
    margin-left: 0.5rem;
}
.btn-new:hover {
    background: var(--bg-card-hover);
    border-color: var(--border-hover);
    color: var(--text-primary);
}

/* ══════════════════════════════════════════ ALERTAS ═══════════════════════ */
.alert-container { animation: slide-down 0.25s var(--ease); }

@keyframes slide-down {
    from { opacity: 0; transform: translateY(-10px); }
    to   { opacity: 1; transform: translateY(0); }
}

.alert-custom {
    display: flex;
    align-items: flex-start;
    gap: 12px;
    background: rgba(248,81,73,0.08);
    border: 1px solid rgba(248,81,73,0.3);
    border-radius: var(--radius-md);
    padding: 14px 16px;
}

.alert-icon {
    font-size: 1.1rem;
    color: var(--danger);
    flex-shrink: 0;
    padding-top: 1px;
}
.alert-text {
    flex: 1;
    font-size: 0.88rem;
    color: var(--text-primary);
    line-height: 1.5;
}
.alert-close {
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 0.85rem;
    cursor: pointer;
    padding: 2px;
    transition: color var(--dur) var(--ease);
    flex-shrink: 0;
}
.alert-close:hover { color: var(--danger); }

/* ══════════════════════════════════════════ HOW SECTION ════════════════════ */
.how-section {
    background: linear-gradient(180deg, var(--bg-base) 0%, var(--bg-card) 100%);
    border-top: 1px solid var(--border);
}

.section-title {
    font-size: 1.8rem;
    font-weight: 700;
    letter-spacing: -0.03em;
}

.how-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 2rem 1.5rem;
    text-align: center;
    position: relative;
    transition: transform var(--dur) var(--ease),
                border-color var(--dur) var(--ease),
                box-shadow var(--dur) var(--ease);
}
.how-card:hover {
    transform: translateY(-4px);
    border-color: var(--border-hover);
    box-shadow: var(--shadow-card);
}

.how-number {
    position: absolute;
    top: -14px; left: 50%;
    transform: translateX(-50%);
    width: 28px; height: 28px;
    background: var(--grad-primary);
    color: #fff;
    font-size: 0.78rem;
    font-weight: 800;
    border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    box-shadow: 0 0 14px var(--accent-glow);
}

.how-icon {
    font-size: 2.2rem;
    color: var(--accent-light);
    margin-bottom: 1rem;
    display: block;
}

.how-title {
    font-size: 1rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}
.how-desc {
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.6;
    margin: 0;
}

/* ══════════════════════════════════════════ FOOTER ═════════════════════════ */
.footer {
    border-top: 1px solid var(--border);
    background: var(--bg-card);
}
.footer-text {
    font-size: 0.88rem;
    color: var(--text-secondary);
    margin: 0;
}
.footer-sub {
    font-size: 0.78rem;
    color: var(--text-muted);
    margin: 0;
}

/* ══════════════════════════════════════ ANIMACIONES ENTRADA ════════════════ */
.fade-in {
    animation: fade-in 0.3s var(--ease) both;
}
@keyframes fade-in {
    from { opacity: 0; transform: translateY(8px); }
    to   { opacity: 1; transform: translateY(0); }
}

/* ══════════════════════════════════════════ RESPONSIVE ═════════════════════ */
@media (max-width: 576px) {
    .hero-section { padding: 3.5rem 1rem 2.5rem; }
    .hero-title { font-size: 2rem; }
    .hero-stats { gap: 1.5rem; }
    .drop-zone { min-height: 170px; }
    .btn-merge { width: calc(100% - 2rem); margin-inline: 1rem; }
    .btn-download, .btn-new { width: 100%; justify-content: center; margin: 0.25rem 0; }
    .file-item { padding: 8px 10px; gap: 7px; }
    .file-delete-btn { opacity: 1; }
}

@media (max-width: 768px) {
    .container { padding-inline: 1rem; }
    .how-card { padding: 1.75rem 1.25rem; }
}

/* ══════════════════════════════════════ MAIN CONTAINER PADDING ════════════ */
#app { padding-top: 2rem; }