* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

:root {
    --primary-green: #2ecc71;
    --accent-yellow: #f1c40f;
    --dark-green: #27ae60;
    --light-yellow: #fef9e7;
    --light-green: #e8f5e9;
    --dark-text: #2c3e50;
    --light-text: #ecf0f1;
    --card-shadow: 0 10px 20px rgba(0,0,0,0.08);
}

body {
    background: linear-gradient(135deg, var(--light-green), var(--light-yellow));
    min-height: 100vh;
    padding: 20px;
    color: var(--dark-text);
    transition: all 0.3s ease;
}

.container {
    max-width: 480px;
    margin: 0 auto;
    position: relative;
}

header {
    text-align: center;
    padding: 30px 20px;
    position: relative;
    overflow: hidden;
    border-radius: 20px;
    background: var(--primary-green);
    color: white;
    box-shadow: var(--card-shadow);
    margin-bottom: 30px;
}

.geometric-shapes {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    z-index: 0;
}

.shape {
    position: absolute;
    background: rgba(255,255,255,0.2);
    border-radius: 50%;
    transition: all 0.5s ease;
}

.shape:nth-child(1) {
    width: 100px;
    height: 100px;
    top: -30px;
    left: -30px;
}

.shape:nth-child(2) {
    width: 70px;
    height: 70px;
    bottom: -20px;
    right: 40px;
}

.shape:nth-child(3) {
    width: 50px;
    height: 50px;
    top: 40px;
    right: -20px;
}

.shape:nth-child(4) {
    width: 40px;
    height: 40px;
    bottom: 50px;
    left: 20px;
}

.title-content {
    position: relative;
    z-index: 1;
}

h1 {
    font-size: 3.5rem;
    font-weight: 800;
    letter-spacing: 2px;
    margin-bottom: 5px;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.2);
}

.subtitle {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 15px;
    letter-spacing: 1px;
}

.description {
    font-size: 0.95rem;
    line-height: 1.6;
    max-width: 400px;
    margin: 0 auto;
    background: rgba(255,255,255,0.2);
    padding: 15px;
    border-radius: 12px;
    backdrop-filter: blur(5px);
}

.notes-section {
    background: white;
    border-radius: 20px;
    padding: 25px 20px;
    box-shadow: 0 8px 20px rgba(0,0,0,0.05);
    margin-bottom: 30px;
}

.section-title {
    font-size: 1.3rem;
    font-weight: 700;
    margin-bottom: 20px;
    color: var(--dark-green);
    display: flex;
    align-items: center;
}

.section-title i {
    margin-right: 10px;
    color: var(--accent-yellow);
}

.subject-list, .chapter-list {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.subject-item, .chapter-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: var(--light-green);
    padding: 18px 20px;
    border-radius: 15px;
    transition: all 0.3s ease;
    cursor: pointer;
    border-left: 5px solid var(--primary-green);
}

.subject-item:hover, .chapter-item:hover {
    transform: translateY(-3px);
    box-shadow: 0 5px 15px rgba(0,0,0,0.1);
    background: white;
    border-left: 5px solid var(--accent-yellow);
}

.subject-name, .chapter-name {
    font-size: 1.1rem;
    font-weight: 600;
}

.subject-icon, .chapter-icon {
    width: 40px;
    height: 40px;
    background: var(--accent-yellow);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 1.2rem;
    color: var(--dark-text);
}

.about-section {
    background: white;
    border-radius: 20px;
    padding: 25px 20px;
    box-shadow: 0 8px 20px rgba(0,0,0,0.05);
    margin-bottom: 30px;
    border-top: 5px solid var(--accent-yellow);
}

.about-content {
    display: flex;
    align-items: center;
    gap: 20px;
}

.avatar {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary-green), var(--dark-green));
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 2.5rem;
    font-weight: bold;
    flex-shrink: 0;
}

.about-text {
    flex: 1;
}

.about-text p {
    line-height: 1.6;
    margin-bottom: 10px;
}

.contact-section {
    background: white;
    border-radius: 20px;
    padding: 25px 20px;
    box-shadow: 0 8px 20px rgba(0,0,0,0.05);
    margin-bottom: 30px;
    border-top: 5px solid var(--primary-green);
}

.social-icons {
    display: flex;
    justify-content: center;
    gap: 25px;
    margin-top: 20px;
}

.social-icon {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background: var(--primary-green);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.5rem;
    transition: all 0.3s ease;
}

.social-icon:hover {
    transform: translateY(-5px) rotate(10deg);
    background: var(--accent-yellow);
}

footer {
    text-align: center;
    padding: 20px;
    color: var(--dark-text);
    font-weight: 500;
}

.back-button {
    position: absolute;
    top: 20px;
    left: 20px;
    color: white;
    font-size: 1.5rem;
    z-index: 2;
    background: rgba(255,255,255,0.2);
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
    transition: all 0.3s ease;
}

.back-button:hover {
    background: rgba(255,255,255,0.3);
    transform: translateX(-5px);
}

.subject-page-header {
    position: relative;
    padding-top: 70px;
}

.chapter-container {
    max-width: 480px;
    margin: 0 auto;
    padding: 20px;
}

.page {
    display: none;
    animation: fadeIn 0.5s ease;
}

.page.active {
    display: block;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

.subject-icon-large {
    font-size: 2rem;
    margin-bottom: 15px;
    color: var(--primary-green);
}

.logo {
    position: absolute;
    top: 15px;
    right: 15px;
    font-weight: bold;
    color: white;
    font-size: 1.2rem;
    z-index: 2;
}

@media (max-width: 480px) {
    h1 {
        font-size: 2.8rem;
    }
    
    .subtitle {
        font-size: 1rem;
    }
    
    .description {
        font-size: 0.9rem;
    }
    
    .avatar {
        width: 70px;
        height: 70px;
        font-size: 2rem;
    }
    
    .subject-name, .chapter-name {
        font-size: 1rem;
    }
}

.contact-section .section-title i {
    transform: scaleX(-1);
}