*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --bg-primary: #0f0f1a;
    --bg-secondary: #1a1a2e;
    --bg-card: #16213e;
    --bg-input: #1e1e3a;
    --border: #2a2a4a;
    --border-hover: #4f46e5;
    --text-primary: #e2e8f0;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --accent: #6366f1;
    --accent-hover: #818cf8;
    --accent-glow: rgba(99, 102, 241, 0.3);
    --success: #22c55e;
    --error: #ef4444;
    --radius: 16px;
    --radius-sm: 10px;
    --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow-x: hidden;
}


.back-btn {
    display: inline-block;
    padding: 12px 30px;
    font-size: 18px;
    font-weight: bold;
    color: #fff;
    text-decoration: none;
    background: #222;
    border: 2px solid #fff;
    border-radius: 8px;
    box-shadow: 0 0 10px #fff33f33;
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.back-btn::before {
    content: '';
    position: absolute;
    top: 50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: rgba(255, 255, 255, 0.2);
    transform: rotate(45deg);
    transition: all 0.5s ease;
}

.back-btn:hover::before {
    left: 100%;
}

.back-btn:hover {
    color: #fff;
    background: #111;
    box-shadow: 0 0 20px #fffa00, 0 0 30px #fffa00, 0 0 40px #fffa00;
    transform: scale(1.05);
}

.bg-particles {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: 0;
}

.particle {
    position: absolute;
    border-radius: 50%;
    background: var(--accent);
    opacity: 0;
    animation: floatUp linear infinite;
}

@keyframes floatUp {
    0% {
        transform: translateY(100vh) scale(0);
        opacity: 0;
    }
    10% {
        opacity: 0.15;
    }
    90% {
        opacity: 0.15;
    }
    100% {
        transform: translateY(-10vh) scale(1);
        opacity: 0;
    }
}

.container {
    position: relative;
    z-index: 1;
    width: 100%;
    max-width: 640px;
    padding: 24px;
}

.header {
    text-align: center;
    margin-bottom: 32px;
    animation: fadeInDown 0.6s ease-out;
}

@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.logo {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 72px;
    height: 72px;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 20px;
    margin-bottom: 16px;
    box-shadow: 0 0 30px var(--accent-glow);
    animation: pulseGlow 3s ease-in-out infinite;
}

@keyframes pulseGlow {
    0%, 100% { box-shadow: 0 0 20px var(--accent-glow); }
    50% { box-shadow: 0 0 40px rgba(99, 102, 241, 0.5); }
}

.logo svg {
    width: 40px;
    height: 40px;
}

.header h1 {
    font-size: 2rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    background: linear-gradient(135deg, #a5b4fc, #818cf8, #6366f1);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-top: 6px;
}

.main-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 32px;
    animation: fadeInUp 0.6s ease-out 0.1s both;
    box-shadow: 0 4px 40px rgba(0, 0, 0, 0.3);
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.upload-zone {
    border: 2px dashed var(--border);
    border-radius: var(--radius);
    padding: 40px 24px;
    text-align: center;
    cursor: pointer;
    transition: all var(--transition);
    position: relative;
    background: var(--bg-input);
}

.upload-zone:hover,
.upload-zone.drag-over {
    border-color: var(--accent);
    background: rgba(99, 102, 241, 0.05);
    box-shadow: 0 0 30px var(--accent-glow);
}

.upload-zone.drag-over {
    transform: scale(1.01);
}

.upload-content {
    pointer-events: none;
}

.upload-icon {
    margin-bottom: 16px;
    animation: bounce 2s ease-in-out infinite;
}

@keyframes bounce {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-8px); }
}

.upload-text {
    font-size: 1.15rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 6px;
}

.upload-hint {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 12px;
}

.browse-link {
    color: var(--accent);
    text-decoration: underline;
    cursor: pointer;
    font-weight: 500;
}

.format-hint {
    font-size: 0.75rem;
    color: var(--text-muted);
    line-height: 1.5;
}

.file-info {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 16px;
    background: var(--bg-input);
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    animation: fadeIn 0.3s ease-out;
}

@keyframes fadeIn {
    from { opacity: 0; transform: scale(0.95); }
    to { opacity: 1; transform: scale(1); }
}

.file-icon {
    flex-shrink: 0;
}

.file-details {
    flex: 1;
    min-width: 0;
    text-align: left;
}

.file-name {
    display: block;
    font-weight: 600;
    color: var(--text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.file-size {
    display: block;
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-top: 2px;
}

.remove-file {
    flex-shrink: 0;
    width: 32px;
    height: 32px;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: transparent;
    color: var(--text-secondary);
    font-size: 1.2rem;
    cursor: pointer;
    transition: all var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    line-height: 1;
}

.remove-file:hover {
    border-color: var(--error);
    color: var(--error);
    background: rgba(239, 68, 68, 0.1);
}

.conversion-panel {
    margin-top: 24px;
    animation: fadeIn 0.4s ease-out;
}

.panel-section {
    margin-bottom: 20px;
}

.section-label {
    display: block;
    font-size: 0.8rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-muted);
    margin-bottom: 10px;
}

.source-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 8px 16px;
    background: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: 8px;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--accent);
}

.format-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
    gap: 8px;
}

.format-option {
    padding: 10px 8px;
    background: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--text-secondary);
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition);
    text-align: center;
    text-transform: uppercase;
}

.format-option:hover {
    border-color: var(--accent);
    color: var(--text-primary);
    background: rgba(99, 102, 241, 0.08);
}

.format-option.selected {
    border-color: var(--accent);
    background: rgba(99, 102, 241, 0.15);
    color: var(--accent-hover);
    box-shadow: 0 0 12px var(--accent-glow);
}

.convert-btn {
    width: 100%;
    padding: 14px;
    background: linear-gradient(135deg, #6366f1, #4f46e5);
    border: none;
    border-radius: var(--radius-sm);
    color: #fff;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    letter-spacing: 0.02em;
}

.convert-btn:hover:not(:disabled) {
    background: linear-gradient(135deg, #818cf8, #6366f1);
    box-shadow: 0 4px 20px var(--accent-glow);
    transform: translateY(-1px);
}

.convert-btn:active:not(:disabled) {
    transform: translateY(0);
}

.convert-btn:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}

.progress-section {
    margin-top: 24px;
    animation: fadeIn 0.3s ease-out;
}

.progress-bar {
    width: 100%;
    height: 6px;
    background: var(--bg-input);
    border-radius: 3px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    width: 0%;
    background: linear-gradient(90deg, #6366f1, #818cf8);
    border-radius: 3px;
    transition: width 0.3s ease-out;
    animation: progressPulse 1.5s ease-in-out infinite;
}

@keyframes progressPulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.7; }
}

.progress-text {
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.85rem;
    margin-top: 12px;
}

.result-section,
.error-section {
    margin-top: 24px;
    text-align: center;
    animation: fadeIn 0.4s ease-out;
}

.result-icon {
    margin-bottom: 16px;
}

.result-text {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 20px;
}

.error-text {
    font-size: 0.95rem;
    color: var(--error);
    margin-bottom: 20px;
}

.download-btn {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    padding: 14px 28px;
    background: linear-gradient(135deg, #22c55e, #16a34a);
    border: none;
    border-radius: var(--radius-sm);
    color: #fff;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    text-decoration: none;
    transition: all var(--transition);
    margin-bottom: 12px;
}

.download-btn:hover {
    box-shadow: 0 4px 20px rgba(34, 197, 94, 0.3);
    transform: translateY(-1px);
}

.delete-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 20px;
    background: transparent;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    font-size: 0.85rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition);
    margin-bottom: 12px;
}

.delete-btn:hover {
    border-color: var(--error);
    color: var(--error);
    background: rgba(239, 68, 68, 0.08);
}

.delete-btn:disabled {
    opacity: 0.6;
    cursor: default;
}

.convert-another {
    display: block;
    margin: 0 auto;
    padding: 10px 24px;
    background: transparent;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    font-size: 0.9rem;
    cursor: pointer;
    transition: all var(--transition);
}

.convert-another:hover {
    border-color: var(--accent);
    color: var(--text-primary);
}

.footer {
    text-align: center;
    margin-top: 24px;
    color: var(--text-muted);
    font-size: 0.8rem;
    animation: fadeIn 0.6s ease-out 0.3s both;
}

@media (max-width: 480px) {
    .container {
        padding: 16px;
    }
    .main-card {
        padding: 20px;
    }
    .header h1 {
        font-size: 1.5rem;
    }
    .format-grid {
        grid-template-columns: repeat(auto-fill, minmax(80px, 1fr));
    }
}