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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
        "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.container {
    background: white;
    border-radius: 16px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
    padding: 40px;
    max-width: 900px;
    width: 100%;
}

h1 {
    text-align: center;
    color: #333;
    margin-bottom: 8px;
    font-size: 28px;
}

.subtitle {
    text-align: center;
    color: #666;
    margin-bottom: 30px;
    font-size: 14px;
}

.upload-area {
    border: 2px dashed #ddd;
    border-radius: 12px;
    padding: 60px 20px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s;
    margin-bottom: 20px;
}

.upload-area:hover,
.upload-area.dragover {
    border-color: #667eea;
    background: #f5f7ff;
}

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

.upload-area p {
    color: #666;
    font-size: 16px;
}

.upload-area .hint {
    color: #999;
    font-size: 12px;
    margin-top: 8px;
}

.preview-area {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 30px;
    margin-bottom: 20px;
    flex-wrap: wrap;
}

.image-box {
    text-align: center;
}

.image-box h3 {
    font-size: 14px;
    color: #666;
    margin-bottom: 10px;
}

.image-box img {
    max-width: 300px;
    max-height: 300px;
    border-radius: 8px;
    border: 1px solid #eee;
}

.checkerboard {
    background: conic-gradient(#ccc 0 25%, #fff 0 50%, #ccc 0 75%, #fff 0) 0 0 / 20px 20px;
    border-radius: 8px;
    padding: 10px;
}

.checkerboard img {
    border: none;
}

.arrow {
    font-size: 32px;
    color: #667eea;
}

.loading {
    text-align: center;
    padding: 30px;
}

.spinner {
    width: 40px;
    height: 40px;
    border: 4px solid #f3f3f3;
    border-top: 4px solid #667eea;
    border-radius: 50%;
    margin: 0 auto 16px;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.download-area {
    text-align: center;
    margin-top: 20px;
}

.btn-download {
    display: inline-block;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 12px 32px;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 500;
    margin-right: 10px;
    transition: transform 0.2s;
}

.btn-download:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(102, 126, 234, 0.4);
}

.btn-reset {
    background: #f5f5f5;
    color: #666;
    border: none;
    padding: 12px 24px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 14px;
    transition: background 0.2s;
}

.btn-reset:hover {
    background: #eee;
}

.error-msg {
    background: #ffebee;
    color: #c62828;
    padding: 12px;
    border-radius: 8px;
    text-align: center;
    margin-top: 16px;
}

.hidden {
    display: none !important;
}