/* 全局样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #4a6ea9;
    --secondary-color: #3a5a89;
    --accent-color: #f7b801;
    --success-color: #4caf50;
    --warning-color: #ff9800;
    --danger-color: #f44336;
    --light-color: #f8f9fa;
    --dark-color: #343a40;
    --text-color: #333;
    --light-gray: #f5f5f5;
    --medium-gray: #e9ecef;
    --dark-gray: #6c757d;
    --border-radius: 12px;
    --box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
    --transition: all 0.3s ease;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--light-color);
    background-image: linear-gradient(120deg, #fdfbfb 0%, #ebedee 100%);
}

/* 头部样式 */
header {
    background-color: var(--primary-color);
    color: white;
    text-align: center;
    padding: 2.5rem 1rem;
    position: relative;
    overflow: hidden;
}

header::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, rgba(74, 110, 169, 0.8) 0%, rgba(58, 90, 137, 0.9) 100%);
    z-index: 1;
}

header .container {
    position: relative;
    z-index: 2;
}

header h1 {
    font-size: 3rem;
    margin-bottom: 0.5rem;
    font-weight: 700;
    letter-spacing: -0.5px;
}

header p {
    font-size: 1.2rem;
    opacity: 0.9;
}

/* 导航样式 */
nav {
    background-color: white;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1rem;
}

.language-switcher {
    padding: 1rem;
    margin-left: auto !important;
    display: block;
}

/* 针对RTL语言的样式 */
body[dir="rtl"] .language-switcher {
    margin-left: 0 !important;
    margin-right: auto !important;
    order: 2;
}

body[dir="rtl"] nav ul {
    order: 1;
}

.language-switcher select {
    padding: 0.5rem 1rem;
    border: 1px solid var(--medium-gray);
    border-radius: var(--border-radius);
    background-color: white;
    color: var(--dark-color);
    font-size: 0.9rem;
    cursor: pointer;
    transition: var(--transition);
}

.language-switcher select:hover {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 2px rgba(74, 110, 169, 0.1);
}

nav ul {
    display: flex;
    justify-content: center;
    list-style: none;
    margin: 0;
    padding: 0;
}

nav ul li {
    margin: 0;
    position: relative;
}

nav ul li a {
    color: var(--dark-color);
    text-decoration: none;
    padding: 1.2rem 1.5rem;
    display: block;
    font-weight: 500;
    transition: var(--transition);
}

nav ul li a:hover {
    color: var(--primary-color);
}

nav ul li a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    width: 0;
    height: 3px;
    background-color: var(--primary-color);
    transition: var(--transition);
    transform: translateX(-50%);
}

nav ul li a:hover::after {
    width: 80%;
}

/* 主要内容样式 */
main {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem 1rem;
}

section {
    margin-bottom: 4rem;
    background-color: white;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    padding: 2.5rem;
    transition: var(--transition);
}

section:hover {
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.12);
}

h2 {
    font-size: 2.2rem;
    margin-bottom: 1.5rem;
    color: var(--primary-color);
    position: relative;
    padding-bottom: 0.8rem;
    font-weight: 700;
}

h2::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 80px;
    height: 4px;
    background-color: var(--accent-color);
    border-radius: 2px;
}

#intro {
    text-align: center;
    padding: 3rem 2rem;
    background-color: white;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
}

#intro p {
    font-size: 1.1rem;
    max-width: 800px;
    margin: 0 auto;
    color: var(--dark-gray);
}

/* 级别卡片样式 */
#level-details {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 2rem;
    padding: 2rem 0;
    margin: 0 auto;
    max-width: 1200px;
}

.level-card {
    background-color: white;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    padding: 2rem;
    text-align: center;
    transition: var(--transition);
    flex: 1 1 calc(33.33% - 2rem);
    min-width: 280px;
    max-width: 400px;
    margin: 0;
    position: relative;
    overflow: hidden;
    height: 100%;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

/* 媒体查询 - 针对移动设备 */
@media (max-width: 992px) {
    .level-card {
        flex: 1 1 calc(50% - 2rem);
    }
}

@media (max-width: 768px) {
    .level-card {
        flex: 1 1 100%;
        max-width: 100%;
        padding: 1.5rem;
    }
    
    .level-card h3 {
        font-size: 1.5rem;
    }
    
    .level-features li {
        font-size: 0.9rem;
    }
}

.level-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 5px;
}

.level-card:nth-child(1)::before {
    background-color: var(--primary-color);
}

.level-card:nth-child(2)::before {
    background-color: var(--success-color);
}

.level-card:nth-child(3)::before {
    background-color: var(--warning-color);
}

.level-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 15px 30px rgba(0, 0, 0, 0.15);
}

.level-card h3 {
    color: var(--dark-color);
    margin-bottom: 1rem;
    font-size: 1.8rem;
    font-weight: 600;
}

.level-card p {
    color: var(--dark-gray);
    margin-bottom: 1.5rem;
}

.level-features {
    text-align: left;
    margin-bottom: 1.5rem;
    list-style: none;
}

.level-features li {
    margin-bottom: 0.8rem;
    padding-left: 1.5rem;
    position: relative;
    color: var(--dark-gray);
}

.level-features li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--success-color);
    font-weight: bold;
}

/* 按钮样式 */
button {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: 30px;
    cursor: pointer;
    font-size: 1rem;
    transition: var(--transition);
    font-weight: 500;
    box-shadow: 0 4px 15px rgba(74, 110, 169, 0.2);
}

button:hover {
    background-color: var(--secondary-color);
    transform: translateY(-3px);
    box-shadow: 0 6px 20px rgba(74, 110, 169, 0.3);
}

.start-level {
    margin-top: 1rem;
}

/* 字符和词语卡片样式 */
.character-card, .word-card {
    background-color: white;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    padding: 2rem;
    margin-bottom: 1.5rem;
    text-align: center;
    display: inline-block;
    margin-right: 1rem;
    width: calc(33.33% - 1rem);
    vertical-align: top;
    transition: var(--transition);
}

.character-card:hover, .word-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
}

.character {
    font-size: 3.5rem;
    margin-bottom: 1rem;
    color: var(--primary-color);
    font-weight: bold;
}

.word {
    font-size: 2.2rem;
    margin-bottom: 1rem;
    color: var(--primary-color);
    font-weight: bold;
}

.pinyin {
    font-size: 1.2rem;
    color: var(--dark-gray);
    margin-bottom: 0.5rem;
}

.meaning {
    font-size: 1rem;
    color: var(--text-color);
}

.audio-btn {
    margin-top: 1rem;
    background-color: var(--light-gray);
    color: var(--primary-color);
    width: 45px;
    height: 45px;
    padding: 0;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-left: auto;
    margin-right: auto;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
}

.audio-btn:hover {
    background-color: var(--medium-gray);
    transform: scale(1.05);
}

/* 翻译工具样式 */
.translation-tool {
    background-color: white;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    padding: 2rem;
}

#source-lang {
    padding: 0.8rem 1.2rem;
    margin-bottom: 1rem;
    width: 100%;
    border: 1px solid var(--medium-gray);
    border-radius: var(--border-radius);
    font-size: 1rem;
    transition: var(--transition);
}

#source-lang:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(74, 110, 169, 0.1);
}

#source-text {
    width: 100%;
    height: 180px;
    padding: 1rem 1.2rem;
    margin-bottom: 1rem;
    border: 1px solid var(--medium-gray);
    border-radius: var(--border-radius);
    resize: none;
    font-size: 1rem;
    transition: var(--transition);
}

#source-text:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(74, 110, 169, 0.1);
}

#translate-btn {
    display: block;
    width: 100%;
    margin-bottom: 1rem;
}

#translation-result {
    padding: 1.2rem;
    border: 1px solid var(--medium-gray);
    border-radius: var(--border-radius);
    min-height: 80px;
    background-color: var(--light-gray);
}

/* 页脚样式 */
footer {
    background-color: var(--dark-color);
    color: white;
    text-align: center;
    padding: 2rem 1rem;
    margin-top: 3rem;
}

footer p {
    opacity: 0.8;
}

/* 响应式调整 */
@media (max-width: 992px) {
    .level-card {
        width: calc(50% - 1.5rem);
    }

    .character-card, .word-card {
        width: calc(50% - 1rem);
    }
}

@media (max-width: 768px) {
    header h1 {
        font-size: 2.5rem;
    }

    #level-details {
        flex-wrap: wrap;
        overflow-x: visible;
    }

    .level-card {
        width: 100%;
        margin-bottom: 1.5rem;
    }

    .character-card, .word-card {
        width: 100%;
        margin-right: 0;
    }

    nav ul {
        flex-direction: column;
        align-items: center;
    }

    nav ul li {
        margin: 0;
        width: 100%;
        text-align: center;
    }

    section {
        padding: 1.5rem;
    }
}

@media (max-width: 576px) {
    header h1 {
        font-size: 2rem;
    }

    h2 {
        font-size: 1.8rem;
    }

    .character {
        font-size: 2.8rem;
    }

    .word {
        font-size: 1.8rem;
    }
}