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

:root {
    --primary-color: #0052D9;
    --primary-hover: #003CAB;
    --primary-light: #E8F3FF;
    --success-color: #2BA471;
    --warning-color: #ED7B2F;
    --error-color: #D54941;
    --bg-color: #F2F3F5;
    --card-bg: #ffffff;
    --text-primary: #1A1A1A;
    --text-secondary: #858585;
    --text-tertiary: #BBBBBB;
    --border-color: #DCDCDC;
    --shadow-sm: 0 1px 4px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 2px 8px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 4px 16px rgba(0, 0, 0, 0.1);
    --radius: 8px;
    --radius-sm: 4px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'Helvetica Neue', Helvetica, Arial, sans-serif;
    background: var(--bg-color);
    min-height: 100vh;
    padding: 24px;
    color: var(--text-primary);
    line-height: 1.5;
}

.container {
    max-width: 960px;
    margin: 0 auto;
    background: var(--card-bg);
    border-radius: var(--radius);
    box-shadow: var(--shadow-md);
    overflow: hidden;
}

/* Header */
header {
    background: white;
    color: var(--text-primary);
    padding: 32px 40px;
    text-align: center;
    border-bottom: 1px solid var(--border-color);
}

header h1 {
    font-size: 28px;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.subtitle {
    font-size: 14px;
    color: var(--text-secondary);
    font-weight: 400;
}

/* Main Content */
main {
    padding: 32px 40px;
}

section {
    margin-bottom: 24px;
}

h3 {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 12px;
    color: var(--text-primary);
}

/* Upload Section */
.upload-area {
    border: 2px dashed var(--primary-color);
    border-radius: var(--radius);
    padding: 48px 20px;
    text-align: center;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    background: white;
}

.upload-area:hover {
    border-color: var(--primary-hover);
    background: var(--primary-light);
}

.upload-area.dragover {
    border-color: var(--primary-hover);
    background: var(--primary-light);
    transform: scale(1.01);
}

.upload-icon {
    color: var(--primary-color);
    margin-bottom: 12px;
}

.upload-text {
    font-size: 16px;
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 4px;
}

.upload-subtext {
    font-size: 13px;
    color: var(--text-secondary);
}

/* Preview Section */
.preview-container {
    background: var(--bg-color);
    border-radius: var(--radius);
    padding: 24px;
    text-align: center;
    position: relative;
}

#previewImage {
    max-width: 100%;
    max-height: 300px;
    border-radius: var(--radius-sm);
    box-shadow: var(--shadow-sm);
    background: white;
}

.file-info {
    margin-top: 12px;
    padding: 8px 16px;
    background: white;
    border-radius: var(--radius-sm);
    display: inline-block;
    font-size: 13px;
    color: var(--text-secondary);
    box-shadow: var(--shadow-sm);
}

.btn-remove {
    position: absolute;
    top: 12px;
    right: 12px;
    background: var(--error-color);
    color: white;
    border: none;
    padding: 6px 12px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 13px;
    font-weight: 500;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.btn-remove:hover {
    background: #B9352E;
    transform: translateY(-1px);
}

/* Options Section */
.option-group {
    background: var(--bg-color);
    border-radius: var(--radius);
    padding: 20px;
    margin-bottom: 16px;
}

.option-label {
    display: block;
    font-weight: 500;
    margin-bottom: 12px;
    color: var(--text-primary);
    cursor: pointer;
    font-size: 14px;
}

.option-label input[type="checkbox"] {
    margin-right: 8px;
    cursor: pointer;
    width: 16px;
    height: 16px;
    vertical-align: middle;
    accent-color: var(--primary-color);
}

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

.size-checkbox {
    display: block;
    background: white;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 12px 8px;
    text-align: center;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.size-checkbox:hover {
    border-color: var(--primary-color);
}

.size-checkbox input[type="checkbox"] {
    display: none;
}

.size-checkbox span {
    font-size: 13px;
    font-weight: 400;
    color: var(--text-primary);
}

.size-checkbox input:checked + span {
    color: var(--primary-color);
    font-weight: 500;
}

.size-checkbox:has(input:checked) {
    border-color: var(--primary-color);
    background: var(--primary-light);
}

/* Buttons */
.btn-primary,
.btn-download,
.btn-secondary {
    width: 100%;
    padding: 12px 24px;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
}

.btn-primary:active {
    transform: translateY(0);
}

.btn-download {
    background: var(--success-color);
    color: white;
    margin-bottom: 8px;
}

.btn-download:hover {
    background: #249363;
    transform: translateY(-1px);
}

.btn-secondary {
    background: white;
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

/* Download Section */
.success-message {
    background: #E8F6F0;
    border: 1px solid var(--success-color);
    border-radius: var(--radius);
    padding: 16px 20px;
    text-align: center;
    margin-bottom: 16px;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.success-message svg {
    color: var(--success-color);
}

.success-message p {
    font-size: 15px;
    font-weight: 500;
    color: var(--success-color);
}

.download-options {
    background: var(--bg-color);
    border-radius: var(--radius);
    padding: 20px;
    margin-bottom: 16px;
}

.radio-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.radio-label {
    display: block;
    background: white;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 14px 16px;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.radio-label:hover {
    border-color: var(--primary-color);
}

.radio-label input[type="radio"] {
    display: none;
}

.radio-content strong {
    display: block;
    font-size: 14px;
    color: var(--text-primary);
    margin-bottom: 4px;
    font-weight: 500;
}

.radio-content small {
    display: block;
    font-size: 12px;
    color: var(--text-secondary);
}

.radio-label:has(input:checked) {
    border-color: var(--primary-color);
    background: var(--primary-light);
}

.download-buttons {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

/* Footer */
footer {
    background: var(--bg-color);
    padding: 24px 40px;
    border-top: 1px solid var(--border-color);
}

footer h3 {
    font-size: 14px;
    font-weight: 600;
    margin-bottom: 12px;
}

.instructions {
    margin-bottom: 24px;
}

.instructions ol {
    padding-left: 20px;
}

.instructions li {
    font-size: 13px;
    color: var(--text-secondary);
    margin-bottom: 6px;
    line-height: 1.6;
}

.supported-formats .format-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.format-tag {
    display: inline-block;
    background: var(--primary-color);
    color: white;
    padding: 5px 12px;
    border-radius: var(--radius-sm);
    font-size: 12px;
    font-weight: 500;
}

/* Copyright */
.copyright {
    background: white;
    padding: 20px 40px;
    border-top: 1px solid var(--border-color);
    text-align: center;
}

.copyright p {
    font-size: 12px;
    color: var(--text-tertiary);
    font-weight: 400;
}

/* Responsive */
@media (max-width: 640px) {
    body {
        padding: 16px;
    }

    .container {
        border-radius: var(--radius);
    }

    header {
        padding: 24px 20px;
    }

    header h1 {
        font-size: 22px;
    }

    main {
        padding: 24px 20px;
    }

    .upload-area {
        padding: 36px 20px;
    }

    .size-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    footer {
        padding: 20px;
    }

    .copyright {
        padding: 16px 20px;
    }
}