/* --- 默认明亮主题 --- */
:root {
    --primary-color: #007bff;
    --tool-bg: #f0f2f5;
    --panel-bg: #ffffff;
    --border-color: #dee2e6;
    --text-primary: #212934;
    --text-secondary: #6c757d;
    --input-bg: #ffffff;
    --action-color: #198754;
    --secondary-btn-bg: #6c757d;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: var(--tool-bg);
    color: var(--text-primary);
    margin: 0;
    padding: 20px;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    transition: background-color 0.3s ease, color 0.3s ease;
}

.container {
    width: 100%;
    max-width: 600px;
}

.main-panel {
    background-color: var(--panel-bg);
    padding: 30px;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    text-align: center;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

h2 { margin-top: 0; }
.description { color: var(--text-secondary); margin-bottom: 20px; }

.upload-area-container {
    border: 2px dashed var(--border-color);
    padding: 20px;
    text-align: center;
    border-radius: 12px;
    cursor: pointer;
    transition: all .3s;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}
.upload-area-container:hover, .upload-area-container.dragover {
    border-color: var(--primary-color);
    background-color: #f8faff;
}
.upload-area-container .upload-icon { width: 40px; height: 40px; margin-bottom: 10px; color: var(--text-secondary); }
.upload-area-container .upload-text { font-size: 16px; font-weight: 500; color: var(--text-primary); margin: 0; }
.upload-area-container .upload-hint { font-size: 14px; color: var(--text-secondary); margin: 0; }
.upload-area-container .upload-button-alt { margin-top: 10px; font-size: 14px; padding: 8px 15px; background-color: var(--secondary-btn-bg); color: white; border: none; border-radius: 5px; }

.preview-area { margin-top: 20px; }
.image-wrapper { max-height: 300px; margin-bottom: 10px; display: flex; justify-content: center; align-items: center; }
#imagePreview { max-width: 100%; max-height: 300px; border-radius: 4px; background-color: white; }
#imageInfo { font-size: 14px; color: var(--text-secondary); }

.options-area { margin-top: 20px; }
.options-area h3 { font-size: 16px; margin-bottom: 10px; text-align: left; }

.format-selector { display: flex; justify-content: center; gap: 10px; margin-bottom: 20px; }
.format-btn {
    padding: 8px 16px;
    border: 1px solid var(--border-color);
    background-color: var(--tool-bg);
    color: var(--text-primary);
    border-radius: 20px;
    cursor: pointer;
    font-size: 14px;
    transition: all 0.2s;
}
.format-btn.active, .format-btn:hover {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.option-group { text-align: left; }
.action-area { margin-top: 20px; }

.action-button {
    background: var(--action-color);
    color: white;
    border: none;
    padding: 12px 25px;
    border-radius: 5px;
    cursor: pointer;
    font-size: 16px;
    text-decoration: none;
    display: inline-block;
    margin: 0 5px;
}
.action-button.disabled {
    background-color: #aaa;
    color: #fff;
    cursor: not-allowed;
}

.loader-wrapper { text-align: center; padding: 20px; }
.loader { border: 4px solid #e9ecef; border-top: 4px solid var(--primary-color); border-radius: 50%; width: 40px; height: 40px; animation: spin 1s linear infinite; margin: 0 auto 10px; }
@keyframes spin { 0% { transform: rotate(0deg); } 100% { transform: rotate(360deg); } }

.resolution-inputs { display: flex; align-items: center; justify-content: center; gap: 10px; margin-top: 5px; }
.resolution-inputs input[type="number"] {
    width: 100px;
    padding: 8px;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    text-align: center;
    background-color: var(--input-bg);
    color: var(--text-primary);
}
.lock-icon { font-size: 20px; cursor: pointer; padding: 5px; user-select: none; }
.lock-icon.locked { opacity: 1; color: var(--primary-color); }
.lock-icon:not(.locked) { opacity: 0.5; }

/* --- 暗黑模式覆盖 --- */
body.dark-mode {
    --primary-color: #3d8bfd;
    --tool-bg: #1e2128;
    --panel-bg: #2a2e37;
    --border-color: #4a505f;
    --text-primary: #e5e7eb;
    --text-secondary: #9ca3af;
    --input-bg: #373c47;
    --action-color: #20c997;
    --secondary-btn-bg: #4a505f;
}

body.dark-mode .upload-area-container:hover,
body.dark-mode .upload-area-container.dragover {
    background-color: var(--tool-bg);
}

body.dark-mode .action-button.disabled {
    background-color: #555;
    color: #888;
}

body.dark-mode .loader {
    border-color: #444;
    border-top-color: var(--primary-color);
}