:root {
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --bg-color: #f8fafc;
    --text-color: #1e293b;
    --card-bg: #ffffff;
    --border-color: #e2e8f0;
    --header-height: 70px;
    --radius-lg: 16px;
    --radius-md: 8px;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.1);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.1);
    --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
}

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

body {
    font-family: var(--font-sans);
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.5;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
header {
    height: var(--header-height);
    background-color: var(--card-bg);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 40px;
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 10;
}

.logo-container img.logo {
    height: 32px;
    vertical-align: middle;
    transition: transform 0.2s;
}

.logo-container img.logo:hover {
    transform: scale(1.05);
}

.app-title {
    font-weight: 700;
    font-size: 1.125rem;
    color: var(--text-color);
    letter-spacing: -0.025em;
}

/* Main Content */
main {
    flex: 1;
    max-width: 1000px;
    width: 100%;
    margin: 0 auto;
    padding: 60px 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
}

/* Hero Section */
.hero {
    text-align: center;
    margin-bottom: 48px;
}

.hero h1 {
    font-size: 4rem;
    font-weight: 800;
    letter-spacing: -0.05em;
    margin-bottom: 12px;
    color: #0f172a;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 16px;
}

.hero h1 .arrow {
    color: var(--primary-color);
    font-weight: 300;
}

.hero .subtitle {
    font-size: 1.5rem;
    color: #64748b;
    font-weight: 500;
}

/* Upload Section */
.upload-section {
    width: 100%;
    max-width: 700px;
    height: 300px;
    background-color: var(--card-bg);
    border: 2px dashed var(--border-color);
    border-radius: var(--radius-lg);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
    cursor: pointer;
    margin-bottom: 40px;
}

.upload-section:hover, .upload-section.drag-over {
    border-color: var(--primary-color);
    background-color: #eff6ff;
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.upload-content {
    text-align: center;
}

.upload-content .icon {
    font-size: 48px;
    margin-bottom: 16px;
    opacity: 0.8;
}

.upload-content p {
    font-size: 1.125rem;
    color: #475569;
    margin-bottom: 12px;
}

.upload-content .or {
    display: block;
    font-size: 0.875rem;
    color: #94a3b8;
    margin-bottom: 12px;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 24px;
    border-radius: var(--radius-md);
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    border: none;
    font-size: 1rem;
}

.btn.primary {
    background-color: var(--primary-color);
    color: white;
    box-shadow: 0 2px 4px rgba(59, 130, 246, 0.3);
}

.btn.primary:hover {
    background-color: var(--primary-hover);
    box-shadow: 0 4px 6px rgba(59, 130, 246, 0.4);
}

/* File List Section */
.list-section {
    width: 100%;
    max-width: 700px;
}

.file-list {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.file-item {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 16px;
    display: flex;
    align-items: center;
    gap: 20px;
    box-shadow: var(--shadow-sm);
    animation: slideIn 0.3s ease-out;
}

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

.thumbnail-area {
    width: 100px;
    height: 70px;
    background: #f1f5f9;
    border-radius: 4px;
    overflow: hidden;
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
}

.thumbnail-area img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.thumbnail-area .placeholder {
    font-size: 24px;
}

.info-area {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.file-name {
    font-weight: 600;
    font-size: 0.95rem;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    max-width: 300px;
}

.progress-container {
    width: 100%;
    height: 8px;
    background-color: #f1f5f9;
    border-radius: 4px;
    overflow: hidden;
    position: relative;
}

.progress-bar {
    position: absolute;
    left: 0;
    top: 0;
    height: 100%;
    background-color: var(--primary-color);
    width: 0%;
    transition: width 0.1s linear;
}

.status-text {
    font-size: 0.8rem;
    color: #64748b;
    text-align: right;
    margin-top: 4px;
}

.action-area {
    min-width: 100px;
    display: flex;
    justify-content: flex-end;
}

.download-link {
    display: inline-flex;
    align-items: center;
    padding: 8px 16px;
    background-color: #10b981;
    color: white;
    border-radius: 6px;
    text-decoration: none;
    font-weight: 500;
    font-size: 0.9rem;
    transition: background-color 0.2s;
}

.download-link:hover {
    background-color: #059669;
}

.download-link.disabled {
    background-color: #cbd5e1;
    pointer-events: none;
    cursor: default;
}

/* Floating Banner */
.floating-banner {
    position: fixed;
    right: 20px;
    top: 50%;
    transform: translateY(-50%);
    background: linear-gradient(135deg, #6366f1, #8b5cf6);
    color: white;
    padding: 16px 24px;
    border-radius: 50px;
    text-decoration: none;
    font-weight: 700;
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.4);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    z-index: 100;
    font-size: 1rem;
    display: flex;
    align-items: center;
    gap: 8px;
    border: 2px solid rgba(255, 255, 255, 0.2);
}

.floating-banner:hover {
    transform: translateY(-50%) scale(1.05) translateX(-5px);
    box-shadow: 0 8px 25px rgba(99, 102, 241, 0.6);
    background: linear-gradient(135deg, #4f46e5, #7c3aed);
}

.floating-banner::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border-radius: 50px;
    background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
    transform: translateX(-100%);
    transition: 0.5s;
}

.floating-banner:hover::after {
    transform: translateX(100%);
}

@media (max-width: 768px) {
    .floating-banner {
        bottom: 20px;
        top: auto;
        right: 50%;
        transform: translateX(50%);
        width: max-content;
    }
    
    .floating-banner:hover {
        transform: translateX(50%) scale(1.05);
    }
}