/* KSR Learner Theme Colors */
:root {
    --primary-color: #2563eb;
    --primary-dark: #1e40af;
    --primary-light: #3b82f6;
    --secondary-color: #10b981;
    --accent-color: #8b5cf6;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --bg-light: #f9fafb;
    --bg-white: #ffffff;
    --border-color: #e5e7eb;
    --success-color: #10b981;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

/* Reset & Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-light);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Navigation */
.navbar {
    background: var(--bg-white);
    box-shadow: var(--shadow-md);
    position: sticky;
    top: 0;
    z-index: 1000;
    padding: 1rem 0;
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary-color);
}

.nav-brand i {
    font-size: 1.8rem;
}

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

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

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

.nav-toggle {
    display: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-primary);
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 6rem 0 8rem;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.hero-content {
    position: relative;
    z-index: 2;
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
    font-weight: 700;
}

.hero p {
    font-size: 1.25rem;
    margin-bottom: 2rem;
    opacity: 0.95;
}

.btn-primary {
    display: inline-block;
    padding: 0.875rem 2rem;
    background: var(--secondary-color);
    color: white;
    text-decoration: none;
    border-radius: 0.5rem;
    font-weight: 600;
    transition: all 0.3s ease;
    box-shadow: var(--shadow-lg);
}

.btn-primary:hover {
    background: #059669;
    transform: translateY(-2px);
    box-shadow: 0 15px 25px -5px rgba(16, 185, 129, 0.3);
}

.hero-waves {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 120px;
    overflow: hidden;
}

.hero-waves svg {
    width: 100%;
    height: 100%;
    fill: var(--bg-light);
}

/* Section Styles */
section {
    padding: 4rem 0;
}

.section-title {
    text-align: center;
    font-size: 2.5rem;
    color: var(--text-primary);
    margin-bottom: 1rem;
    font-weight: 700;
}

.section-subtitle {
    text-align: center;
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: 3rem;
}

/* OS Download Sections */
.os-download-section {
    background: var(--bg-white);
    border-radius: 1.5rem;
    padding: 2.5rem;
    margin-bottom: 2.5rem;
    box-shadow: var(--shadow-md);
    transition: all 0.3s ease;
    border: 2px solid transparent;
}

.os-download-section:hover {
    box-shadow: var(--shadow-lg);
    border-color: var(--border-color);
    transform: translateY(-3px);
}

.os-header {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    margin-bottom: 2rem;
    padding-bottom: 1.5rem;
    border-bottom: 2px solid var(--border-color);
}

.os-icon {
    width: 80px;
    height: 80px;
    border-radius: 1.25rem;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2.5rem;
    color: white;
    flex-shrink: 0;
}

.os-icon.android {
    background: linear-gradient(135deg, #3DDC84, #34A853);
}

.os-icon.windows {
    background: linear-gradient(135deg, #0078D4, #00BCF2);
}

.os-icon.ios {
    background: linear-gradient(135deg, #000000, #1D1D1F);
}

.os-info h3 {
    font-size: 2rem;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
    font-weight: 700;
}

.os-info p {
    color: var(--text-secondary);
    font-size: 1rem;
}

.os-details {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    align-items: start;
}

.os-features {
    display: grid;
    gap: 1rem;
}

.feature-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.feature-item i {
    color: var(--success-color);
    font-size: 1.125rem;
}

.feature-item span {
    color: var(--text-primary);
    font-size: 1rem;
}

.os-download {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.download-buttons-group {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.download-buttons-group .btn-download-large {
    flex: 1;
    min-width: 200px;
}

.btn-app-store {
    background: #000000 !important;
}

.btn-app-store:hover {
    background: #1D1D1F !important;
}

.download-info {
    display: flex;
    gap: 1.5rem;
    margin-bottom: 0.5rem;
}

.download-info span {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.download-info i {
    color: var(--primary-color);
}

.btn-download-large {
    padding: 1.25rem 2rem;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 0.75rem;
    cursor: pointer;
    font-weight: 600;
    font-size: 1.125rem;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    transition: all 0.3s ease;
    text-decoration: none;
    box-shadow: var(--shadow-md);
}

.btn-download-large:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-download-large:active {
    transform: translateY(0);
}

.btn-download-large i {
    font-size: 1.5rem;
}

.download-note {
    font-size: 0.875rem;
    color: var(--text-secondary);
    text-align: center;
    margin-top: 0.5rem;
    font-style: italic;
}

.file-size {
    color: var(--text-secondary);
    font-weight: 500;
}

/* Resources Section */
.resources-section {
    background: var(--bg-white);
}

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

.resource-box {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-light));
    padding: 2.5rem;
    border-radius: 1rem;
    text-align: center;
    color: white;
    transition: all 0.3s ease;
}

.resource-box:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.resource-box i {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.resource-box h3 {
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
}

.resource-box p {
    opacity: 0.9;
}

/* About Section */
.about-section {
    background: var(--bg-light);
}

.about-content {
    max-width: 800px;
    margin: 0 auto;
    text-align: center;
}

.about-content h2 {
    font-size: 2.5rem;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.about-content > p {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    line-height: 1.8;
}

.about-features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
    margin-top: 2rem;
}

.feature {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 1rem;
    background: var(--bg-white);
    border-radius: 0.5rem;
    box-shadow: var(--shadow-sm);
}

.feature i {
    color: var(--success-color);
    font-size: 1.5rem;
}

/* Footer */
.footer {
    background: var(--text-primary);
    color: white;
    padding: 3rem 0 1rem;
}

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

.footer-section h3,
.footer-section h4 {
    margin-bottom: 1rem;
}

.footer-section p {
    opacity: 0.8;
    line-height: 1.8;
}

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

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

.footer-section a {
    color: white;
    text-decoration: none;
    opacity: 0.8;
    transition: opacity 0.3s ease;
}

.footer-section a:hover {
    opacity: 1;
}

.social-links {
    display: flex;
    gap: 1rem;
}

.social-links a {
    width: 40px;
    height: 40px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
}

.social-links a:hover {
    background: var(--primary-color);
    transform: translateY(-3px);
}

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    opacity: 0.8;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    z-index: 2000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(5px);
}

.modal-content {
    background-color: var(--bg-white);
    margin: 15% auto;
    padding: 2rem;
    border-radius: 1rem;
    max-width: 500px;
    position: relative;
    box-shadow: var(--shadow-lg);
    animation: modalSlideIn 0.3s ease;
}

@keyframes modalSlideIn {
    from {
        transform: translateY(-50px);
        opacity: 0;
    }
    to {
        transform: translateY(0);
        opacity: 1;
    }
}

.close {
    color: var(--text-secondary);
    float: right;
    font-size: 2rem;
    font-weight: bold;
    cursor: pointer;
    position: absolute;
    right: 1rem;
    top: 1rem;
}

.close:hover {
    color: var(--text-primary);
}

.modal-body {
    text-align: center;
    padding: 1rem;
}

.modal-icon {
    font-size: 4rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.modal-body h3 {
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
}

.modal-body p {
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
}

.download-progress {
    width: 100%;
    height: 8px;
    background: var(--border-color);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 1.5rem;
}

.progress-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    width: 0%;
    transition: width 0.3s ease;
    animation: progressAnimation 2s ease-in-out infinite;
}

@keyframes progressAnimation {
    0%, 100% { width: 0%; }
    50% { width: 70%; }
}

.btn-cancel {
    padding: 0.75rem 1.5rem;
    background: var(--border-color);
    color: var(--text-primary);
    border: none;
    border-radius: 0.5rem;
    cursor: pointer;
    font-weight: 500;
    transition: all 0.3s ease;
}

.btn-cancel:hover {
    background: var(--text-secondary);
    color: white;
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        left: -100%;
        top: 70px;
        flex-direction: column;
        background-color: var(--bg-white);
        width: 100%;
        text-align: center;
        transition: 0.3s;
        box-shadow: var(--shadow-md);
        padding: 2rem 0;
    }

    .nav-menu.active {
        left: 0;
    }

    .nav-toggle {
        display: block;
    }

    .hero h1 {
        font-size: 2rem;
    }

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

    .section-title {
        font-size: 2rem;
    }

    .os-download-section {
        padding: 1.5rem;
    }

    .os-header {
        flex-direction: column;
        text-align: center;
        gap: 1rem;
    }

    .os-icon {
        width: 70px;
        height: 70px;
        font-size: 2rem;
    }

    .os-info h3 {
        font-size: 1.75rem;
    }

    .os-details {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

    .download-info {
        flex-direction: column;
        gap: 0.75rem;
        align-items: center;
    }

    .download-buttons-group {
        flex-direction: column;
    }

    .download-buttons-group .btn-download-large {
        width: 100%;
        min-width: auto;
    }

    .btn-download-large {
        padding: 1rem 1.5rem;
        font-size: 1rem;
    }
}

@media (max-width: 480px) {
    .hero {
        padding: 4rem 0 6rem;
    }

    .hero h1 {
        font-size: 1.75rem;
    }

    .os-download-section {
        padding: 1.25rem;
    }

    .os-icon {
        width: 60px;
        height: 60px;
        font-size: 1.75rem;
    }

    .os-info h3 {
        font-size: 1.5rem;
    }

    .btn-download-large {
        padding: 0.875rem 1.25rem;
        font-size: 0.9375rem;
    }
}