:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --background: #f8fafc;
    --card-bg: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --header-bg: #ffffff;
    --footer-bg: #1e293b;
    --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
}

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

body {
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--background);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

main {
    flex: 1;
}

.navbar {
    background-color: var(--header-bg);
    padding: 1rem 5%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: var(--shadow);
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
}

.logo a {
    color: var(--primary-color);
    text-decoration: none;
    font-size: 1.5rem;
    font-weight: bold;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.logo a i {
    font-size: 1.3rem;
}

.nav-links {
    display: flex;
    list-style: none;
}

.nav-links li {
    margin-left: 2rem;
}

.nav-links a {
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s ease;
}

.nav-links a:hover {
    color: var(--primary-color);
}

.hero {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-hover));
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    color: white;
    padding: 0 1rem;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    width: 200%;
    height: 200%;
    background: url('data:image/svg+xml,<svg width="20" height="20" viewBox="0 0 20 20" xmlns="http://www.w3.org/2000/svg"><circle cx="10" cy="10" r="1" fill="rgba(255,255,255,0.1)"/></svg>');
    animation: float 20s linear infinite;
    opacity: 0.5;
}

@keyframes float {
    0% { transform: translateY(0) rotate(0deg); }
    100% { transform: translateY(-50%) rotate(360deg); }
}

.hero-content {
    max-width: 800px;
    position: relative;
    z-index: 1;
}

.hero h1 {
    font-size: 3.5rem;
    margin-bottom: 1rem;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.1);
}

.hero p {
    font-size: 1.2rem;
    margin-bottom: 2rem;
    text-shadow: 1px 1px 2px rgba(0,0,0,0.1);
}

.cta-button {
    display: inline-block;
    padding: 1rem 2rem;
    background-color: white;
    color: var(--primary-color);
    text-decoration: none;
    border-radius: 50px;
    font-weight: bold;
    transition: all 0.3s ease;
    box-shadow: var(--shadow-lg);
}

.cta-button:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
}

.features {
    padding: 5rem 5%;
    background-color: var(--card-bg);
}

.features h2 {
    text-align: center;
    margin-bottom: 3rem;
    color: var(--primary-color);
    font-size: 2.5rem;
}

.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
}

.feature-card {
    background: var(--card-bg);
    padding: 2rem;
    border-radius: 20px;
    text-align: center;
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
    border: 2px solid var(--border-color);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

.feature-card:hover {
    transform: translateY(-5px);
    border-color: var(--primary-color);
}

.feature-card i {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.feature-card h3 {
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.feature-card p {
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    flex-grow: 1;
}

.feature-link {
    display: inline-block;
    padding: 0.5rem 1.5rem;
    background-color: var(--primary-color);
    color: white;
    text-decoration: none;
    border-radius: 50px;
    transition: all 0.3s ease;
    font-weight: 500;
}

.feature-link:hover {
    background-color: var(--primary-hover);
    transform: translateY(-2px);
}

footer {
    background-color: var(--footer-bg);
    color: white;
    padding: 3rem 5% 1rem;
    position: relative;
    overflow: hidden;
    margin-top: auto;
}

footer::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-color), var(--primary-hover));
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-section h3 {
    margin-bottom: 1rem;
    color: white;
}

.footer-section ul {
    list-style: none;
}

.footer-section ul li {
    margin-bottom: 0.5rem;
}

.footer-section a {
    color: white;
    text-decoration: none;
    transition: color 0.3s ease;
}

.footer-section a:hover {
    color: var(--primary-color);
}

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid rgba(255,255,255,0.1);
}

.burger {
    display: none;
    cursor: pointer;
}

.burger div {
    width: 25px;
    height: 3px;
    background-color: var(--primary-color);
    margin: 5px;
    transition: all 0.3s ease;
    border-radius: 3px;
}

@media screen and (max-width: 768px) {
    .nav-links {
        position: fixed;
        right: -100%;
        top: 70px;
        height: calc(100vh - 70px);
        background-color: var(--header-bg);
        flex-direction: column;
        width: 100%;
        text-align: center;
        transition: 0.5s;
        box-shadow: var(--shadow-lg);
    }

    .nav-links li {
        margin: 2rem 0;
    }

    .burger {
        display: block;
    }

    .hero h1 {
        font-size: 2.5rem;
    }

    .hero p {
        font-size: 1rem;
    }
}

.nav-active {
    right: 0;
}

@keyframes navLinkFade {
    from {
        opacity: 0;
        transform: translateX(50px);
    }
    to {
        opacity: 1;
        transform: translateX(0px);
    }
}

.category-section {
    margin-bottom: 4rem;
}

.category-section h3 {
    color: var(--primary-color);
    font-size: 1.8rem;
    margin-bottom: 2rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--border-color);
}

.category-section:last-child {
    margin-bottom: 0;
} 

.calculator-container {
    max-width: 800px;
    margin: 100px auto 50px;
    padding: 2rem;
    background: var(--card-bg);
    border-radius: 20px;
    box-shadow: var(--shadow);
}

.calculator-form {
    display: grid;
    gap: 1.5rem;
    margin-top: 2rem;
}

.form-group {
    display: grid;
    gap: 0.5rem;
}

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

.form-group input,
.form-group select,
.form-group textarea {
    padding: 0.75rem;
    border: 2px solid var(--border-color);
    border-radius: 10px;
    font-size: 1rem;
    transition: all 0.3s ease;
}

.form-group textarea {
    min-height: 200px;
    resize: vertical;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary-color);
}

.calculator-button {
    padding: 1rem;
    font-size: 1.1rem;
    border: none;
    border-radius: 10px;
    background: var(--primary-color);
    color: white;
    cursor: pointer;
    transition: all 0.3s ease;
}

.calculator-button:hover {
    background: var(--primary-hover);
}

.result {
    margin-top: 2rem;
    padding: 1.5rem;
    background: var(--background);
    border-radius: 10px;
    text-align: center;
}

.result.hidden {
    display: none;
}

.result-value {
    font-size: 2rem;
    font-weight: bold;
    color: var(--primary-color);
    margin: 1rem 0;
}

.result-details {
    display: grid;
    gap: 0.5rem;
    margin-top: 1rem;
    color: var(--text-secondary);
}

.premium-value,
.grade-value {
    font-size: 2rem;
    font-weight: bold;
    color: var(--primary-color);
    margin: 1rem 0;
}

.info-container {
    margin-top: 2rem;
    padding: 1.5rem;
    background: var(--background);
    border-radius: 10px;
    text-align: left;
}

.info-container h3 {
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.info-container ul {
    list-style-type: none;
    padding: 0;
}

.info-container li {
    margin-bottom: 0.5rem;
    color: var(--text-secondary);
}

.info-container li:before {
    content: "•";
    color: var(--primary-color);
    font-weight: bold;
    display: inline-block;
    width: 1em;
    margin-left: -1em;
}

.premium-details,
.grade-details {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
    margin-top: 1.5rem;
}

.detail-card {
    padding: 1rem;
    background: var(--card-bg);
    border-radius: 10px;
    text-align: center;
}

.detail-card h4 {
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.detail-card p {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.add-course {
    margin-top: 1rem;
    padding: 0.5rem;
    background: var(--background);
    border: none;
    border-radius: 5px;
    color: var(--primary-color);
    cursor: pointer;
    transition: all 0.3s ease;
}

.add-course:hover {
    background: var(--card-bg);
}

.course-row {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 1rem;
    margin-bottom: 1rem;
}

.remove-course {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all 0.3s ease;
}

.remove-course:hover {
    color: var(--primary-color);
}

.info-text {
    margin-top: 1rem;
    color: var(--text-secondary);
    font-size: 0.9rem;
    text-align: center;
}

.time-container {
    max-width: 800px;
    margin: 100px auto 50px;
    padding: 2rem;
    background: var(--card-bg);
    border-radius: 20px;
    box-shadow: var(--shadow);
}

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

.time-section {
    padding: 1.5rem;
    background: var(--background);
    border-radius: 10px;
    text-align: center;
}

.time-section h2 {
    color: var(--text-primary);
    margin-bottom: 1rem;
    font-size: 1.2rem;
}

.time-value {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary-color);
    margin: 1rem 0;
    word-break: break-all;
}

.time-label {
    color: var(--text-secondary);
    font-size: 0.9rem;
}