:root {
    --bg-color: #050608;
    --panel-bg: rgba(20, 20, 20, 0.9);
    --panel-border: #333;
    --accent: #2a6fff;
    --text-main: #f5f5f5;
    --text-muted: #aaa;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    padding: 0;
    background: var(--bg-color);
    color: var(--text-main);
    font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    overflow: hidden;
}

/* 顶部小条 */
.top-bar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: 40px;
    display: flex;
    align-items: center;
    padding: 0 12px;
    background: rgba(0, 0, 0, 0.9);
    z-index: 10;
}

.top-bar .brand {
    font-size: 14px;
    font-weight: 600;
}

.top-bar .spacer {
    flex: 1;
}

.top-btn {
    background: #3baf2a;
    border: none;
    color: white;
    padding: 6px 12px;
    border-radius: 3px;
    font-size: 12px;
    cursor: pointer;
}

/* 左侧控制面板 + 右侧大画布 */
.layout {
    position: fixed;
    top: 40px;
    bottom: 0;
    left: 0;
    right: 0;
    display: flex;
}

.left-panel {
    flex: 0 0 320px;
    min-width: 320px;
    padding: 16px;
    background: var(--panel-bg);
    border-right: 1px solid var(--panel-border);
    display: flex;
    flex-direction: column;
    gap: 16px;
    z-index: 5;
    overflow-y: auto;
}

.panel-block {
    border: 1px solid var(--panel-border);
    border-radius: 6px;
    padding: 10px 10px 12px;
}

.panel-block h3 {
    margin: 0 0 8px;
    font-size: 13px;
    color: var(--text-muted);
}

.panel-block button {
    margin-top: 10px;
    width: 100%;
    padding: 6px 0;
    font-size: 12px;
    border-radius: 4px;
    border: none;
    cursor: pointer;
    background: var(--accent);
    color: white;
}

.button-row {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
}

#btnRandom {
    background: #ffffff;
    color: #000000;
}

.block-header {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    gap: 6px;
    margin-bottom: 6px;
}

.block-header .muted {
    color: var(--text-muted);
    font-size: 11px;
}

.input-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
}

.input-grid label {
    display: flex;
    flex-direction: column;
    gap: 4px;
    padding: 6px;
    border-radius: 6px;
    background: #0b0d10;
    border: 1px solid #1e1e1e;
    font-size: 12px;
    color: var(--text-muted);
}

.input-grid input {
    width: 100%;
    padding: 6px 8px;
    font-size: 12px;
    border-radius: 4px;
    border: 1px solid #2f2f2f;
    background: #15171c;
    color: var(--text-main);
}

.checkbox-row {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 12px;
    padding: 4px 0;
    color: var(--text-main);
}

.checkbox-row input {
    width: 14px;
    height: 14px;
    accent-color: var(--accent);
}

.link-count-row {
    margin-bottom: 8px;
    font-size: 12px;
    color: var(--text-main);
}

.link-count-row input {
    margin-left: 8px;
    width: 64px;
    padding: 6px 8px;
    font-size: 12px;
    border-radius: 4px;
    border: 1px solid #2f2f2f;
    background: #15171c;
    color: var(--text-main);
}

/* 右侧画布占满剩余空间 */
#pendulumCanvas {
    flex: 1;
    display: block;
    width: 100%;
    height: 100%;
}