/* --- 默认明亮主题 --- */
:root {
    --primary-color: #007bff;
    --tool-bg: #f8f9fa;
    --panel-bg: #ffffff;
    --border-color: #dee2e6;
    --text-primary: #212529;
    --text-secondary: #6c757d;
    --input-bg: #ffffff;
    --success-color: #198754;
    --secondary-btn-bg: #6c757d;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    margin: 0;
    background-color: var(--tool-bg);
    color: var(--text-primary);
    display: flex;
    justify-content: center;
    align-items: flex-start;
    padding: 20px;
    min-height: 100vh;
    box-sizing: border-box;
    /* 新增：为主题切换增加平滑过渡 */
    transition: background-color 0.3s ease, color 0.3s ease;
}

.container {
    display: flex;
    width: 100%;
    max-width: 1400px;
    gap: 20px;
    background: var(--panel-bg);
    padding: 20px;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

.controls {
    width: 320px;
    min-width: 320px;
    flex-shrink: 0;
    display: flex;
    flex-direction: column;
    gap: 15px;
}

h1 { font-size: 24px; margin-bottom: 0; }
.description { font-size: 13px; color: var(--text-secondary); margin-bottom: 10px; }
.control-group { display: flex; flex-direction: column; gap: 8px; }
label { font-weight: 500; font-size: 14px; }

input[type="text"], select {
    width: 100%; padding: 8px; border: 1px solid var(--border-color);
    border-radius: 4px; font-size: 14px; background-color: var(--input-bg); color: var(--text-primary);
}

input[type="color"] {
    width: 100%; height: 38px; border: 1px solid var(--border-color);
    border-radius: 4px; padding: 4px; background-color: var(--input-bg);
}

input[type="range"] { width: 100%; cursor: pointer; }

button {
    width: 100%; padding: 10px; background-color: var(--primary-color); color: white;
    border: none; border-radius: 4px; cursor: pointer; font-size: 16px;
    text-align: center; transition: background-color 0.2s;
}
button:hover { background-color: #0b5ed7; }

.file-upload-area {
    border: 2px dashed var(--border-color); background-color: var(--tool-bg);
    color: var(--text-secondary); padding: 20px;
}
.file-upload-area.dragover { background-color: #e9ecef; border-color: var(--primary-color); }
.file-upload-area p { margin: 0 0 10px 0; pointer-events: none; }
.file-upload-area button { background-color: var(--secondary-btn-bg); }
.file-upload-area button:hover { background-color: #5a6268; }

.radio-group { display: flex; gap: 10px; align-items: center; }
.radio-group label { font-weight: normal; }

.position-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 5px; }
.pos-btn { height: 30px; background-color: var(--tool-bg); border: 1px solid var(--border-color); color: var(--text-primary); }
.pos-btn:hover { background-color: #e9ecef; }

.download-button { background-color: var(--success-color); }
.download-button:hover { background-color: #157347; }

hr { border: none; border-top: 1px solid var(--border-color); margin: 10px 0; }

.canvas-container {
    flex-grow: 1; display: flex; justify-content: center; align-items: center;
    background-color: var(--tool-bg); border-radius: 8px; min-height: 400px;
    position: relative; overflow: hidden;
    /* 明亮棋盘格 */
    background-image: linear-gradient(45deg, #eee 25%, transparent 25%), linear-gradient(-45deg, #eee 25%, transparent 25%), linear-gradient(45deg, transparent 75%, #eee 75%), linear-gradient(-45deg, transparent 75%, #eee 75%);
    background-size: 20px 20px;
    background-position: 0 0, 0 10px, 10px -10px, -10px 0px;
}
#canvas { max-width: 100%; max-height: 80vh; object-fit: contain; cursor: move; }
#placeholderText { color: var(--text-secondary); font-size: 18px; position: absolute; }
.checkbox-group { display: flex; align-items: center; gap: 8px; }
.checkbox-group label { cursor: pointer; }

@media (max-width: 900px) {
    body { padding: 0; }
    .container { flex-direction: column; border-radius: 0; padding: 10px; }
    .controls { width: 100%; }
    #canvas { max-height: 60vh; }
}

/* --- 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;
    --success-color: #20c997;
    --secondary-btn-bg: #4a505f;
}

body.dark-mode button:hover { background-color: #4c9aff; }
body.dark-mode .file-upload-area.dragover { background-color: #2a2e37; border-color: var(--primary-color); }
body.dark-mode .file-upload-area button:hover { background-color: #5a6268; }
body.dark-mode .pos-btn:hover { background-color: #2a2e37; }
body.dark-mode .download-button:hover { background-color: #15b37e; }

body.dark-mode .canvas-container {
    /* 暗色棋盘格 */
    background-image: linear-gradient(45deg, #2a2e37 25%, transparent 25%), linear-gradient(-45deg, #2a2e37 25%, transparent 25%), linear-gradient(45deg, transparent 75%, #2a2e37 75%), linear-gradient(-45deg, transparent 75%, #2a2e37 75%);
}