/* ============ 全局变量 ============ */
:root {
    --lego-yellow: #FFB400;
    --lego-red: #E53935;
    --lego-blue: #1E88E5;
    --lego-green: #43A047;
    --lego-orange: #FB8C00;
    --soft-bg: #FFF8E7;
    --soft-bg-2: #E3F2FD;
    --text-dark: #2D2D2D;
    --text-mid: #555;
    --text-light: #888;
    --shadow-soft: 0 4px 14px rgba(0, 0, 0, 0.08);
    --shadow-pop: 0 8px 24px rgba(0, 0, 0, 0.15);
    --radius-card: 18px;
    --radius-btn: 12px;
    --font-kid: "Comic Sans MS", "Microsoft YaHei", "PingFang SC", "Helvetica Neue", sans-serif;
}

/* ============ 重置与基础 ============ */
* { box-sizing: border-box; margin: 0; padding: 0; }

body {
    font-family: var(--font-kid);
    background: linear-gradient(135deg, #FFF8E7 0%, #E3F2FD 100%);
    color: var(--text-dark);
    min-height: 100vh;
    line-height: 1.6;
    overflow-x: hidden;
}

.hidden { display: none !important; }

button {
    font-family: inherit;
    cursor: pointer;
    border: none;
    outline: none;
}

/* ============ 顶部导航 ============ */
.top-bar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 24px;
    background: white;
    box-shadow: var(--shadow-soft);
    position: sticky;
    top: 0;
    z-index: 100;
}

.back-home {
    display: flex;
    align-items: center;
    gap: 6px;
    text-decoration: none;
    color: var(--text-dark);
    background: var(--soft-bg);
    padding: 8px 14px;
    border-radius: var(--radius-btn);
    font-weight: bold;
    transition: transform 0.2s, background 0.2s;
}
.back-home:hover { background: var(--lego-yellow); transform: translateY(-2px); }
.back-icon { font-size: 1.2rem; }

.brand {
    display: flex;
    align-items: center;
    gap: 12px;
}
.brand-icon {
    font-size: 2rem;
    animation: bounce 2s infinite;
}
@keyframes bounce {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-6px); }
}
.brand-text h1 {
    font-size: 1.4rem;
    color: var(--lego-red);
    margin: 0;
}
.brand-text p {
    font-size: 0.85rem;
    color: var(--text-mid);
    margin: 0;
}

.progress-mini {
    background: var(--lego-blue);
    color: white;
    padding: 8px 14px;
    border-radius: var(--radius-btn);
    font-weight: bold;
    font-size: 0.95rem;
}

/* ============ Hero 区 ============ */
.home-view {
    max-width: 1100px;
    margin: 0 auto;
    padding: 24px 20px 60px;
}

.hero {
    display: flex;
    align-items: center;
    gap: 30px;
    background: white;
    border-radius: var(--radius-card);
    padding: 30px;
    box-shadow: var(--shadow-soft);
    margin-bottom: 32px;
    flex-wrap: wrap;
}

.hero-art {
    flex: 0 0 220px;
}
.hero-robot {
    width: 100%;
    height: auto;
    animation: floatY 3s ease-in-out infinite;
}
@keyframes floatY {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-10px); }
}

.hero-text {
    flex: 1;
    min-width: 240px;
}
.hero-text h2 {
    font-size: 2rem;
    color: var(--lego-red);
    margin-bottom: 10px;
}
.hero-sub {
    font-size: 1.1rem;
    color: var(--text-mid);
    margin-bottom: 16px;
}
.hero-features {
    list-style: none;
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
}
.hero-features li {
    background: var(--soft-bg);
    padding: 8px 16px;
    border-radius: var(--radius-btn);
    font-size: 0.95rem;
    font-weight: bold;
}

/* ============ 课程卡片网格 ============ */
.section-heading {
    font-size: 1.5rem;
    margin-bottom: 20px;
    color: var(--text-dark);
}

.lesson-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: 20px;
}

.lesson-card {
    background: white;
    border-radius: var(--radius-card);
    padding: 22px;
    box-shadow: var(--shadow-soft);
    cursor: pointer;
    transition: transform 0.25s, box-shadow 0.25s;
    border-top: 6px solid var(--lego-yellow);
    position: relative;
    overflow: hidden;
}
.lesson-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-pop);
}
.lesson-card.done::before {
    content: '✓';
    position: absolute;
    top: 12px;
    right: 12px;
    background: var(--lego-green);
    color: white;
    width: 28px;
    height: 28px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
}

.lesson-card .lesson-num {
    display: inline-block;
    background: var(--lego-red);
    color: white;
    padding: 4px 12px;
    border-radius: 14px;
    font-size: 0.85rem;
    font-weight: bold;
    margin-bottom: 10px;
}
.lesson-card .lesson-icon {
    font-size: 3rem;
    text-align: center;
    margin: 8px 0;
}
.lesson-card h4 {
    font-size: 1.25rem;
    margin-bottom: 6px;
    color: var(--text-dark);
}
.lesson-card .lesson-sub {
    font-size: 0.9rem;
    color: var(--text-mid);
    margin-bottom: 12px;
}
.lesson-card .lesson-skills {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}
.lesson-card .skill-tag {
    background: var(--soft-bg-2);
    color: var(--lego-blue);
    padding: 3px 10px;
    border-radius: 10px;
    font-size: 0.75rem;
    font-weight: bold;
}

/* ============ 课程详情页 ============ */
.lesson-view {
    max-width: 1100px;
    margin: 0 auto;
    padding: 24px 20px 60px;
}

.lesson-header {
    background: white;
    border-radius: var(--radius-card);
    padding: 24px;
    box-shadow: var(--shadow-soft);
    margin-bottom: 16px;
    display: flex;
    align-items: center;
    gap: 20px;
    flex-wrap: wrap;
}
.lesson-header .header-icon {
    font-size: 4rem;
}
.lesson-header .header-text { flex: 1; min-width: 200px; }
.lesson-header h2 {
    color: var(--lego-red);
    font-size: 1.8rem;
    margin-bottom: 4px;
}
.lesson-header .header-sub {
    color: var(--text-mid);
    font-size: 1rem;
    margin-bottom: 10px;
}
.lesson-header .objectives {
    background: var(--soft-bg);
    padding: 12px 16px;
    border-radius: var(--radius-btn);
    margin-top: 8px;
}
.lesson-header .objectives strong { color: var(--lego-red); }
.lesson-header .objectives ul {
    list-style: none;
    margin-top: 6px;
}
.lesson-header .objectives li::before {
    content: '🎯 ';
}

/* tab 切换 */
.lesson-tabs {
    display: flex;
    gap: 8px;
    margin-bottom: 16px;
    flex-wrap: wrap;
    background: white;
    padding: 8px;
    border-radius: var(--radius-card);
    box-shadow: var(--shadow-soft);
}
.tab-btn {
    background: var(--soft-bg);
    color: var(--text-dark);
    padding: 10px 18px;
    border-radius: var(--radius-btn);
    font-weight: bold;
    font-size: 0.95rem;
    transition: all 0.2s;
}
.tab-btn:hover { background: var(--lego-yellow); }
.tab-btn.active {
    background: var(--lego-red);
    color: white;
}

/* 主内容区 */
.lesson-content {
    background: white;
    border-radius: var(--radius-card);
    padding: 28px;
    box-shadow: var(--shadow-soft);
    min-height: 400px;
    margin-bottom: 20px;
}

.lesson-content h3 {
    color: var(--lego-blue);
    font-size: 1.4rem;
    margin-bottom: 14px;
    display: flex;
    align-items: center;
    gap: 8px;
}

/* 形象记忆法 */
.metaphor-box {
    background: linear-gradient(135deg, #FFE082 0%, #FFD54F 100%);
    padding: 20px;
    border-radius: var(--radius-card);
    margin: 14px 0;
    border-left: 6px solid var(--lego-orange);
}
.metaphor-box p {
    font-size: 1.05rem;
    margin-bottom: 8px;
}
.metaphor-box strong { color: var(--lego-red); }

/* 关键诀窍 */
.tips-box {
    background: #E8F5E9;
    padding: 18px;
    border-radius: var(--radius-card);
    margin: 14px 0;
    border-left: 6px solid var(--lego-green);
}
.tips-box ul {
    list-style: none;
}
.tips-box li {
    padding: 6px 0;
    font-size: 1rem;
}
.tips-box li::before {
    content: '💡 ';
}

/* 步骤 */
.steps-box {
    background: #F3E5F5;
    padding: 20px;
    border-radius: var(--radius-card);
    margin: 14px 0;
}
.step-item {
    display: flex;
    gap: 14px;
    padding: 10px 0;
    border-bottom: 1px dashed #ccc;
}
.step-item:last-child { border-bottom: none; }
.step-num {
    background: var(--lego-blue);
    color: white;
    width: 32px;
    height: 32px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    flex-shrink: 0;
}
.step-text { flex: 1; font-size: 1rem; }

/* 测验 */
.quiz-box {
    margin: 14px 0;
}
.quiz-question {
    background: var(--soft-bg-2);
    padding: 18px;
    border-radius: var(--radius-card);
    margin-bottom: 14px;
}
.quiz-question .q-text {
    font-size: 1.1rem;
    font-weight: bold;
    margin-bottom: 12px;
}
.quiz-options {
    display: flex;
    flex-direction: column;
    gap: 10px;
}
.quiz-option {
    background: white;
    padding: 12px 18px;
    border-radius: var(--radius-btn);
    border: 2px solid #ddd;
    text-align: left;
    transition: all 0.2s;
    font-size: 1rem;
}
.quiz-option:hover {
    border-color: var(--lego-blue);
    transform: translateX(4px);
}
.quiz-option.correct {
    background: #C8E6C9;
    border-color: var(--lego-green);
    color: var(--lego-green);
}
.quiz-option.wrong {
    background: #FFCDD2;
    border-color: var(--lego-red);
    color: var(--lego-red);
}
.quiz-feedback {
    margin-top: 10px;
    padding: 10px;
    border-radius: var(--radius-btn);
    font-weight: bold;
    text-align: center;
}
.quiz-feedback.right { background: #C8E6C9; color: var(--lego-green); }
.quiz-feedback.wrong { background: #FFCDD2; color: var(--lego-red); }
.quiz-score {
    background: var(--lego-yellow);
    padding: 12px;
    border-radius: var(--radius-btn);
    text-align: center;
    font-weight: bold;
    font-size: 1.1rem;
    margin-top: 14px;
}

/* 挑战 */
.challenge-box {
    background: linear-gradient(135deg, #FF6B6B 0%, #E53935 100%);
    color: white;
    padding: 22px;
    border-radius: var(--radius-card);
    margin: 14px 0;
}
.challenge-box h4 {
    font-size: 1.2rem;
    margin-bottom: 10px;
}
.challenge-box .challenge-item {
    background: rgba(255, 255, 255, 0.2);
    padding: 12px;
    border-radius: var(--radius-btn);
    margin-top: 10px;
}

/* 动画演示区 */
.animation-stage {
    background: linear-gradient(180deg, #E3F2FD 0%, #BBDEFB 100%);
    border-radius: var(--radius-card);
    padding: 20px;
    margin: 16px 0;
    text-align: center;
    position: relative;
    overflow: hidden;
}
.animation-stage svg {
    max-width: 100%;
    height: auto;
}
.animation-controls {
    margin-top: 12px;
    display: flex;
    gap: 10px;
    justify-content: center;
    flex-wrap: wrap;
}
.demo-btn {
    background: var(--lego-blue);
    color: white;
    padding: 10px 20px;
    border-radius: var(--radius-btn);
    font-weight: bold;
    transition: transform 0.2s, background 0.2s;
}
.demo-btn:hover { background: #1565C0; transform: translateY(-2px); }
.demo-btn.secondary { background: var(--lego-orange); }
.demo-btn.secondary:hover { background: #EF6C00; }

/* 数学小助手专属 */
.math-helper {
    background: #fff;
    border: 3px solid #333;
    border-radius: var(--radius-card);
    padding: 20px;
    text-align: center;
    margin: 14px 0;
}
.math-screen {
    background: #C8E6C9;
    border: 4px solid #333;
    border-radius: 8px;
    padding: 20px;
    font-family: monospace;
    font-size: 2rem;
    color: #1B5E20;
    margin-bottom: 14px;
    min-height: 80px;
    display: flex;
    align-items: center;
    justify-content: center;
}
.math-input {
    display: flex;
    gap: 8px;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
}
.math-input input {
    width: 100px;
    font-size: 1.5rem;
    padding: 8px;
    border: 2px solid #333;
    border-radius: 8px;
    text-align: center;
    font-family: monospace;
}

/* 底部导航 */
.lesson-nav {
    display: flex;
    justify-content: space-between;
    gap: 10px;
    flex-wrap: wrap;
}
.nav-btn {
    background: white;
    color: var(--text-dark);
    padding: 12px 24px;
    border-radius: var(--radius-btn);
    box-shadow: var(--shadow-soft);
    font-weight: bold;
    font-size: 1rem;
    transition: all 0.2s;
}
.nav-btn:hover {
    background: var(--lego-yellow);
    transform: translateY(-2px);
}
.nav-btn:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}
.nav-btn.home-btn {
    background: var(--lego-blue);
    color: white;
}
.nav-btn.home-btn:hover { background: #1565C0; color: white; }

/* 弹窗 */
.modal {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.6);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    animation: fadeIn 0.3s;
}
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }
.modal-content {
    background: white;
    border-radius: var(--radius-card);
    padding: 36px;
    text-align: center;
    max-width: 400px;
    width: 90%;
    box-shadow: var(--shadow-pop);
    animation: pop 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
}
@keyframes pop {
    from { transform: scale(0.7); opacity: 0; }
    to { transform: scale(1); opacity: 1; }
}
.celebrate-emoji { font-size: 5rem; margin-bottom: 14px; animation: spin 1.2s linear; }
@keyframes spin { from { transform: rotate(0); } to { transform: rotate(360deg); } }
.modal-content h2 { color: var(--lego-red); margin-bottom: 10px; font-size: 1.8rem; }
.modal-content p { color: var(--text-mid); margin-bottom: 20px; font-size: 1.1rem; }
.modal-btn {
    background: var(--lego-green);
    color: white;
    padding: 12px 30px;
    border-radius: var(--radius-btn);
    font-weight: bold;
    font-size: 1.1rem;
    transition: transform 0.2s;
}
.modal-btn:hover { transform: scale(1.05); }

/* 通用图示文本 */
.caption {
    font-style: italic;
    color: var(--text-mid);
    font-size: 0.9rem;
    margin-top: 8px;
}

/* ====== EV3 部件演示交互 ====== */
.ev3-parts-info {
    background: white;
    padding: 14px;
    border-radius: var(--radius-card);
    margin-top: 12px;
    min-height: 60px;
    font-size: 1.05rem;
    text-align: center;
}
.ev3-parts-info strong { color: var(--lego-red); }
.ev3-part {
    cursor: pointer;
    transition: filter 0.2s;
}
.ev3-part:hover { filter: brightness(1.2) drop-shadow(0 0 5px gold); }
.ev3-part.selected { filter: drop-shadow(0 0 8px var(--lego-red)); }

/* ====== SVG 共用样式 ====== */
.bot-body { fill: var(--lego-yellow); stroke: #333; stroke-width: 3; }
.bot-track { fill: #333; }
.bot-track-circle { fill: #888; }
.bot-screen { fill: white; stroke: #333; stroke-width: 2; }
.bot-sensor { fill: var(--lego-red); stroke: #333; stroke-width: 2; }

/* 移动设备 */
@media (max-width: 700px) {
    .brand-text h1 { font-size: 1.1rem; }
    .brand-text p { font-size: 0.75rem; }
    .hero { padding: 20px; }
    .hero-art { flex: 0 0 160px; margin: 0 auto; }
    .hero-text h2 { font-size: 1.5rem; }
    .lesson-content { padding: 18px; }
    .lesson-header { padding: 18px; }
    .lesson-header h2 { font-size: 1.4rem; }
    .lesson-tabs { padding: 6px; }
    .tab-btn { padding: 8px 12px; font-size: 0.85rem; }
    .nav-btn { padding: 10px 14px; font-size: 0.9rem; }
}