/* ===========================
   CSS 變數與基礎設定 (參考 LinearRegration)
   =========================== */
:root {
    /* 主色調 */
    --primary: #6366f1;
    --primary-light: #818cf8;
    --primary-dark: #4f46e5;

    /* 類別顏色 */
    --point-color: #f43f5e;
    --point-glow: rgba(244, 63, 94, 0.4);
    --line-color: #06b6d4;

    /* 背景與表面 */
    --bg-gradient-start: #0f172a;
    --bg-gradient-end: #1e293b;
    --surface: rgba(30, 41, 59, 0.8);
    --surface-light: rgba(51, 65, 85, 0.6);
    --glass: rgba(255, 255, 255, 0.05);
    --glass-border: rgba(255, 255, 255, 0.1);

    /* 文字 */
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;

    /* 其他 */
    --radius: 16px;
    --radius-sm: 8px;
    --shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: 'Noto Sans TC', -apple-system, BlinkMacSystemFont, sans-serif;
    background: linear-gradient(135deg, var(--bg-gradient-start), var(--bg-gradient-end));
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.6;
    padding-bottom: 50px;
}

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 2rem;
}

/* ===========================
   頁首
   =========================== */
header {
    text-align: center;
    margin-bottom: 2rem;
    padding: 1.5rem;
    background: var(--glass);
    border-radius: var(--radius);
    border: 1px solid var(--glass-border);
    backdrop-filter: blur(10px);
}

header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary-light), var(--line-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 0.5rem;
    text-shadow: none;
    /* 移除舊陰影 */
}

header p {
    color: var(--text-secondary);
    font-size: 1.1rem;
    opacity: 1;
}

/* ===========================
   核心視覺化區域
   =========================== */
.main-content {
    background: transparent;
    /* 移除舊背景 */
    box-shadow: none;
    /* 移除舊陰影 */
    border-radius: 0;
    padding: 0;
    min-height: auto;
}

.visualization-area {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

/* 控制面板 */
.controls-panel {
    background: var(--surface);
    padding: 1.5rem;
    border-radius: var(--radius);
    border: 1px solid var(--glass-border);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow);
}

.control-group {
    display: flex;
    align-items: center;
    gap: 1rem;
    flex-wrap: wrap;
}

.control-group label {
    color: var(--text-secondary);
    font-weight: 500;
}

/* 按鈕樣式 (Filter & Size & Padding) */
.btn-filter,
.btn-size,
.btn-padding {
    padding: 0.6rem 1.2rem;
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-sm);
    background: var(--surface-light);
    color: var(--text-primary);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
    cursor: pointer;
    font-weight: 500;
    transition: var(--transition);
}

.btn-filter:hover,
.btn-size:hover,
.btn-padding:hover {
    background: var(--glass-border);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

.btn-filter.active,
.btn-size.active,
.btn-padding.active {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    border-color: transparent;
    color: white;
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.3);
}

/* 畫布容器 */
.canvas-container {
    display: grid;
    grid-template-columns: 1fr 300px 1fr;
    gap: 2rem;
    align-items: start;
    background: var(--surface);
    /* 統一背景 */
    padding: 2rem;
    border-radius: var(--radius);
    border: 1px solid var(--glass-border);
    box-shadow: var(--shadow);
}

.canvas-box {
    text-align: center;
    background: transparent;
}

.canvas-box h3,
.canvas-box h4 {
    margin-bottom: 1rem;
    color: var(--text-secondary);
    font-weight: 600;
}

canvas {
    background: white;
    /* 保持白色以顯示圖像 */
    border-radius: var(--radius-sm);
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.3);
    cursor: crosshair;
    image-rendering: pixelated;
    max-width: 100%;
}

/* 運算細節面板 (中間層) */
.math-panel {
    background: var(--glass);
    border-radius: var(--radius);
    padding: 1.5rem;
    border: 1px solid var(--glass-border);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1.5rem;
}

.kernel-grid {
    display: grid;
    /* grid-template-columns 由 JS 動態控制 */
    gap: 5px;
    background: rgba(255, 255, 255, 0.1);
    padding: 10px;
    border-radius: var(--radius-sm);
}

.kernel-cell {
    width: 35px;
    height: 35px;
    background: var(--surface-light);
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: monospace;
    font-weight: bold;
    font-size: 0.9rem;
    border-radius: 4px;
    border: 1px solid var(--glass-border);
}

/* 卷積運算過程 (獨立面板) */
.calculation-panel {
    background: var(--surface);
    padding: 1.5rem;
    border-radius: var(--radius);
    border: 1px solid var(--glass-border);
    margin-top: 0;
    /* 在 grid gap 中處理間距 */
    box-shadow: var(--shadow);
}

.calculation-panel h4 {
    margin-bottom: 1rem;
    color: var(--text-secondary);
}

.math-expression {
    font-family: monospace;
    background: rgba(0, 0, 0, 0.3);
    padding: 1.5rem;
    border-radius: var(--radius-sm);
    width: 100%;
    text-align: left;
    font-size: 0.95rem;
    line-height: 1.8;
    border: 1px solid var(--glass-border);
    min-height: 100px;
    color: var(--text-primary);
}

/* ===========================
   下方教學說明區域
   =========================== */
.info-section {
    margin-top: 3rem;
}

.info-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.5rem;
}

.info-card {
    background: var(--surface);
    padding: 1.5rem;
    border-radius: var(--radius);
    border: 1px solid var(--glass-border);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow);
}

.info-card h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 1rem;
    background: linear-gradient(135deg, var(--primary-light), var(--line-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.info-card p,
.info-list li {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

.info-card p {
    margin-bottom: 0.8rem;
}

.info-list {
    list-style: none;
    padding-left: 0;
}

.info-list li {
    position: relative;
    padding-left: 1.2rem;
    margin-bottom: 0.5rem;
}

.info-list li::before {
    content: "•";
    position: absolute;
    left: 0;
    color: var(--primary);
    font-weight: bold;
}

/* ===========================
   頁尾
   =========================== */
.footer {
    text-align: center;
    padding: 2rem 0;
    margin-top: 3rem;
    color: var(--text-muted);
    font-size: 0.9rem;
    border-top: 1px solid var(--glass-border);
}

.back-home {
    display: inline-block;
    margin-top: 1rem;
    padding: 0.6rem 1.5rem;
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
    text-decoration: none;
    border-radius: 50px;
    font-weight: 500;
    font-size: 0.9rem;
    transition: var(--transition);
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.3);
    border: none;
}

.back-home:hover {
    transform: translateY(-3px);
    background: linear-gradient(135deg, var(--primary), var(--primary-light));
    box-shadow: 0 6px 25px rgba(99, 102, 241, 0.5);
    color: white;
}

/* 返回首頁連結 */
.back-link {
    display: inline-block;
    margin-top: 2rem;
    padding: 0.6rem 1.5rem;
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
    text-decoration: none;
    border-radius: 50px;
    font-weight: 500;
    font-size: 0.9rem;
    transition: var(--transition);
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.3);
    border: none;
}

.back-link:hover {
    transform: translateY(-3px);
    background: linear-gradient(135deg, var(--primary), var(--primary-light));
    box-shadow: 0 6px 25px rgba(99, 102, 241, 0.5);
    color: white;
}

/* 響應式設計 */
@media (max-width: 1200px) {
    .canvas-container {
        grid-template-columns: 1fr;
        max-width: 600px;
        margin: 0 auto;
    }

    .math-panel {
        order: -1;
        /* 中間層移到最上面 */
        margin: 0;
    }
}

@media (max-width: 768px) {
    .container {
        padding: 1rem;
    }

    header h1 {
        font-size: 1.75rem;
    }

    .control-group {
        justify-content: center;
    }
}

/* 響應式設計補充 */
@media (max-width: 1024px) {
    .info-grid {
        grid-template-columns: 1fr;
    }
}