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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
}

header {
    background: linear-gradient(135deg, #667eea 0%, #ff6b6b 100%);
    color: white;
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

.logo {
    font-size: 1.8rem;
    font-weight: bold;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: text-shadow 0.2s ease;
}

.logo:hover {
    text-shadow: 0 0 15px #ff6b6b, 0 0 25px #ff6b6b;
    cursor: default;
}

@keyframes electricGlow {
    0% {
        filter: drop-shadow(0 0 5px rgba(255, 255, 255, 0.8));
    }
    50% {
        filter: drop-shadow(0 0 15px rgba(255, 255, 255, 1)) drop-shadow(0 0 20px #ff6b6b);
    }
    100% {
        filter: drop-shadow(0 0 5px rgba(255, 255, 255, 0.8));
    }
}

.logo img {
    height: 50px;
    width: auto;
    vertical-align: middle;
    margin-right: 10px;
    animation: electricGlow 2s infinite ease-in-out;
}

nav ul {
    display: flex;
    list-style: none;
    gap: 2rem;
}

nav a {
    color: white;
    text-decoration: none;
    transition: opacity 0.3s;
}

nav a:hover {
    opacity: 0.8;
}

.user-profile {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: white;
    cursor: default;
}

.profile-pic {
    width: 30px;
    height: 30px;
    border-radius: 50%;
    background-color: #333;
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 1rem;
}

.user-name {
    font-size: 1rem;
}

.hero {
    background: linear-gradient(135deg, #667eea 0%, #ff6b6b 100%);
    color: white;
    padding: 4rem 2rem;
    text-align: center;
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.hero p {
    font-size: 1.3rem;
    margin-bottom: 2rem;
}

.btn {
    display: inline-block;
    padding: 1rem 2.5rem;
    background: linear-gradient(135deg, #667eea 0%, #ff6b6b 100%);
    color: white;
    text-decoration: none;
    border-radius: 50px;
    font-weight: 600;
    font-size: 1.1rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    box-shadow: 0 4px 15px rgba(255, 107, 107, 0.4);
    transition: all 0.3s ease;
    border: 2px solid transparent;
    position: relative;
    overflow: hidden;
}

.btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.5s;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(255, 107, 107, 0.6);
    border-color: rgba(255, 255, 255, 0.3);
}

.btn:hover::before {
    left: 100%;
}

.btn:active {
    transform: translateY(0);
    box-shadow: 0 2px 10px rgba(255, 107, 107, 0.4);
}

.btn-secondary {
    display: inline-block;
    padding: 1rem 2.5rem;
    background: #f8fafc;
    color: #111827;
    text-decoration: none;
    border-radius: 50px;
    font-weight: 600;
    font-size: 1.1rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    border: 2px solid #cbd5e1;
    transition: all 0.3s ease;
}

.btn-secondary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(15, 23, 42, 0.08);
    border-color: #94a3b8;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
}

.completion-panel {
    margin-top: 2rem;
}

.completion-panel-box {
    background: #f0fdf4;
    border: 1px solid #d1fae5;
    border-radius: 16px;
    padding: 1.5rem;
    text-align: center;
}

.completion-panel-box p {
    margin-bottom: 1rem;
    color: #064e3b;
}

.courses {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin: 4rem 0;
}

.course-card {
    border: 1px solid #ddd;
    padding: 2rem;
    border-radius: 8px;
    text-align: center;
    transition: box-shadow 0.3s;
}

.course-card:hover {
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.course-card h3 {
    color: #ff6b6b;
    margin-bottom: 1rem;
}

.course-card p {
    margin-bottom: 1.5rem;
}

footer {
    background: #333;
    color: white;
    text-align: center;
    padding: 2rem;
    margin-top: 4rem;
}

.explanation {
    background: #f8f9fa;
    border-radius: 12px;
    padding: 2rem;
    margin: 2rem 0;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.explanation h3 {
    color: #ff6b6b;
    margin-bottom: 1rem;
    font-size: 1.5rem;
}

.explanation p {
    margin-bottom: 1.5rem;
    line-height: 1.7;
    color: #555;
}

.formula {
    font-size: 2rem;
    font-weight: bold;
    color: #333;
    text-align: center;
    background: #fff;
    padding: 1rem;
    border-radius: 8px;
    border: 2px solid #ff6b6b;
    margin: 1rem 0;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.formula-list, .units-list {
    margin: 1rem 0;
    padding-left: 2rem;
}

.formula-list li, .units-list li {
    margin-bottom: 0.5rem;
    color: #555;
}

.formula-list strong, .units-list strong {
    color: #ff6b6b;
}

/* Practice Problems Styles */
.practice-problems {
    margin: 2rem 0;
}

.problem {
    background: #f8f9fa;
    border-radius: 12px;
    padding: 2rem;
    margin: 2rem 0;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.problem h3 {
    color: #ff6b6b;
    margin-bottom: 1rem;
    font-size: 1.5rem;
}

.problem p {
    margin-bottom: 1.5rem;
    line-height: 1.7;
    color: #555;
}

.solution-btn, .submit-btn, .check-btn {
    background: linear-gradient(135deg, #667eea 0%, #ff6b6b 100%);
    color: white;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: 25px;
    cursor: pointer;
    font-weight: 600;
    font-size: 1rem;
    margin: 0.5rem 0;
    transition: all 0.3s ease;
}

.solution-btn:hover, .submit-btn:hover, .check-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(255, 107, 107, 0.4);
}

.check-btn:active {
    transform: translateY(0);
    box-shadow: 0 2px 8px rgba(255, 107, 107, 0.3);
}

.quiz-options {
    margin: 1rem 0;
}

.quiz-options label {
    display: block;
    margin: 0.5rem 0;
    padding: 0.5rem;
    background: #fff;
    border-radius: 8px;
    cursor: pointer;
    transition: background 0.3s;
}

.quiz-options label:hover {
    background: #e9ecef;
}

.quiz-options input[type="radio"] {
    margin-right: 0.5rem;
}

.feedback {
    margin: 1rem 0;
    font-weight: bold;
}

/* Practice Problems Styles */
.practice-problems {
    margin: 2rem 0;
}

.problem {
    background: linear-gradient(135deg, #f8f9fa 0%, #e9ecef 100%);
    border-radius: 12px;
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    border-left: 5px solid #667eea;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.problem:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 15px rgba(0, 0, 0, 0.15);
}

.problem h3 {
    color: #667eea;
    margin-bottom: 1rem;
    font-size: 1.4rem;
}

.problem p {
    margin-bottom: 1.5rem;
    line-height: 1.6;
    color: #555;
}

.solution {
    background: #fff;
    border-radius: 8px;
    padding: 1.5rem;
    margin: 1rem 0;
    border: 2px solid #28a745;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.solution p {
    margin: 0;
    color: #28a745;
    font-weight: 600;
}

.solution-btn {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: 25px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
    position: relative;
    overflow: hidden;
}

.solution-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.5s;
}

.solution-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(102, 126, 234, 0.6);
}

.solution-btn:hover::before {
    left: 100%;
}

.solution-btn:active {
    transform: translateY(0);
    box-shadow: 0 2px 10px rgba(102, 126, 234, 0.4);
}

.next-section {
    text-align: center;
    margin: 3rem 0;
    padding: 2rem;
    background: linear-gradient(135deg, #f8f9fa 0%, #e9ecef 100%);
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.next-section .btn {
    margin: 0 1rem;
    display: inline-block;
}

.back-btn {
    background: linear-gradient(135deg, #6c757d 0%, #495057 100%);
}

.back-btn:hover {
    box-shadow: 0 8px 25px rgba(108, 117, 125, 0.6);
}

/* Circuit Diagram Styles */
.circuit-diagram {
    text-align: center;
    margin: 2rem 0;
    padding: 1rem;
    background: #fff;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    overflow-x: auto;
}

.circuit-diagram svg {
    max-width: 100%;
    height: auto;
    margin-bottom: 0.5rem;
    min-width: 400px;
}

.diagram-caption {
    font-size: 0.9rem;
    color: #666;
    font-style: italic;
    margin-top: 0.5rem;
}