/* === VARIABLES === */
:root {
    --color-primary: #6366f1;
    --color-primary-dark: #4f46e5;
    --color-primary-light: #a5b4fc;
    --color-secondary: #0ea5e9;
    --color-accent: #f59e0b;

    --color-text: #1e293b;
    --color-text-light: #64748b;
    --color-text-lighter: #94a3b8;

    --color-bg: #ffffff;
    --color-bg-soft: #f8fafc;
    --color-bg-muted: #f1f5f9;

    --color-border: #e2e8f0;

    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;

    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.1);

    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --radius-xl: 24px;

    --transition: 150ms ease;
}

/* === RESET === */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    font-size: 16px;
    line-height: 1.6;
    color: var(--color-text);
    background-color: var(--color-bg);
    -webkit-font-smoothing: antialiased;
}

img {
    max-width: 100%;
    height: auto;
}

a {
    color: inherit;
    text-decoration: none;
}

ul {
    list-style: none;
}

/* === UTILITIES === */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

/* === BUTTONS === */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 20px;
    font-size: 15px;
    font-weight: 500;
    border-radius: var(--radius-md);
    transition: all var(--transition);
    cursor: pointer;
    border: none;
}

.btn-primary {
    background: var(--color-primary);
    color: white;
}

.btn-primary:hover {
    background: var(--color-primary-dark);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background: var(--color-bg);
    color: var(--color-text);
    border: 1px solid var(--color-border);
}

.btn-secondary:hover {
    background: var(--color-bg-soft);
    border-color: var(--color-text-lighter);
}

.btn-disabled {
    opacity: 0.6;
    cursor: not-allowed;
    pointer-events: none;
}

.btn-large {
    padding: 14px 28px;
    font-size: 17px;
    border-radius: var(--radius-md);
}

.btn-block {
    width: 100%;
}

/* === NAVIGATION === */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--color-border);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
    height: 70px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 22px;
    font-weight: 700;
    color: var(--color-text);
}

.logo-icon {
    color: var(--color-primary);
    font-size: 24px;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 32px;
}

.nav-links a:not(.btn) {
    font-size: 15px;
    font-weight: 500;
    color: var(--color-text-light);
    transition: color var(--transition);
}

.nav-links a:not(.btn):hover {
    color: var(--color-text);
}

.nav-links .btn {
    margin-left: 8px;
}

/* === HERO === */
.hero {
    padding: 160px 0 80px;
    background: linear-gradient(180deg, var(--color-bg-soft) 0%, var(--color-bg) 100%);
    text-align: center;
    overflow: hidden;
}

.hero-badge {
    display: inline-block;
    padding: 6px 14px;
    background: var(--color-primary-light);
    color: var(--color-primary-dark);
    font-size: 13px;
    font-weight: 600;
    border-radius: 50px;
    margin-bottom: 24px;
}

.hero h1 {
    font-size: clamp(40px, 6vw, 64px);
    font-weight: 700;
    line-height: 1.1;
    margin-bottom: 24px;
    color: var(--color-text);
}

.hero h1 .highlight {
    color: var(--color-primary);
}

.hero-subtitle {
    max-width: 600px;
    margin: 0 auto 32px;
    font-size: 19px;
    line-height: 1.7;
    color: var(--color-text-light);
}

.hero-cta {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
    margin-bottom: 60px;
}

.hero-note {
    font-size: 14px;
    color: var(--color-text-lighter);
}

/* Phone Mockup */
.hero-visual {
    display: flex;
    justify-content: center;
}

.phone-mockup {
    width: 280px;
    height: 560px;
    background: #1e293b;
    border-radius: 40px;
    padding: 12px;
    box-shadow: var(--shadow-xl);
}

.phone-screen {
    width: 100%;
    height: 100%;
    background: white;
    border-radius: 32px;
    overflow: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
}

.survey-preview {
    padding: 32px 24px;
    text-align: center;
}

.survey-header {
    font-size: 13px;
    font-weight: 600;
    color: var(--color-primary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 24px;
}

.survey-question {
    font-size: 20px;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: 32px;
}

.survey-scale {
    display: flex;
    justify-content: center;
    gap: 12px;
    margin-bottom: 32px;
}

.scale-item {
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    background: var(--color-bg-muted);
    border-radius: 50%;
    transition: all var(--transition);
}

.scale-item.active {
    background: var(--color-primary);
    transform: scale(1.15);
    box-shadow: var(--shadow-md);
}

.survey-progress {
    height: 4px;
    background: var(--color-bg-muted);
    border-radius: 2px;
    overflow: hidden;
}

.survey-progress::after {
    content: '';
    display: block;
    width: 40%;
    height: 100%;
    background: var(--color-primary);
    border-radius: 2px;
}

/* === SOCIAL PROOF === */
.social-proof {
    padding: 40px 0;
    border-top: 1px solid var(--color-border);
    border-bottom: 1px solid var(--color-border);
    background: var(--color-bg);
}

.social-proof .container {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 24px;
}

.social-proof p {
    font-size: 14px;
    color: var(--color-text-lighter);
    text-transform: uppercase;
    letter-spacing: 1px;
    font-weight: 500;
}

.logos {
    display: flex;
    gap: 48px;
    flex-wrap: wrap;
    justify-content: center;
}

.university-logo {
    font-size: 16px;
    font-weight: 600;
    color: var(--color-text-lighter);
    opacity: 0.6;
}

/* === PROBLEM SECTION === */
.problem {
    padding: 100px 0;
    background: var(--color-bg);
}

.problem h2 {
    text-align: center;
    font-size: 36px;
    font-weight: 700;
    margin-bottom: 48px;
}

.problem-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 24px;
}

.problem-card {
    padding: 32px;
    background: var(--color-bg-soft);
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
}

.problem-icon {
    font-size: 32px;
    margin-bottom: 16px;
}

.problem-card h3 {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--color-text);
}

.problem-card p {
    font-size: 15px;
    color: var(--color-text-light);
    line-height: 1.6;
}

/* === SOLUTION/FEATURES === */
.solution {
    padding: 100px 0;
    background: var(--color-bg-soft);
}

.solution-header {
    text-align: center;
    margin-bottom: 64px;
}

.solution-header h2 {
    font-size: 36px;
    font-weight: 700;
    margin-bottom: 16px;
}

.solution-header p {
    font-size: 18px;
    color: var(--color-text-light);
    max-width: 560px;
    margin: 0 auto;
}

.feature-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
}

.feature-card {
    padding: 32px;
    background: var(--color-bg);
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
    transition: all var(--transition);
}

.feature-card:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-2px);
}

.feature-card.featured {
    grid-column: span 1;
}

.feature-icon {
    font-size: 32px;
    margin-bottom: 16px;
}

.feature-card h3 {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 12px;
    color: var(--color-text);
}

.feature-card p {
    font-size: 15px;
    color: var(--color-text-light);
    line-height: 1.7;
}

.feature-list {
    margin-top: 20px;
    padding-top: 20px;
    border-top: 1px solid var(--color-border);
}

.feature-list li {
    font-size: 14px;
    color: var(--color-text-light);
    padding: 8px 0;
    padding-left: 24px;
    position: relative;
}

.feature-list li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--color-primary);
    font-weight: 600;
}

/* === PRICING === */
.pricing {
    padding: 100px 0;
    background: var(--color-bg);
}

.pricing-header {
    text-align: center;
    margin-bottom: 64px;
}

.pricing-header h2 {
    font-size: 36px;
    font-weight: 700;
    margin-bottom: 16px;
}

.pricing-header p {
    font-size: 18px;
    color: var(--color-text-light);
}

.pricing-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
    margin-bottom: 48px;
}

.pricing-card {
    padding: 32px 24px;
    background: var(--color-bg);
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
    text-align: center;
    position: relative;
    transition: all var(--transition);
}

.pricing-card:hover {
    box-shadow: var(--shadow-lg);
}

.pricing-card.popular {
    border-color: var(--color-primary);
    box-shadow: 0 0 0 1px var(--color-primary);
}

.popular-badge {
    position: absolute;
    top: -12px;
    left: 50%;
    transform: translateX(-50%);
    background: var(--color-primary);
    color: white;
    font-size: 12px;
    font-weight: 600;
    padding: 4px 12px;
    border-radius: 50px;
    white-space: nowrap;
}

.pricing-tier {
    font-size: 18px;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: 4px;
}

.pricing-participants {
    font-size: 14px;
    color: var(--color-text-light);
    margin-bottom: 20px;
}

.pricing-price {
    margin-bottom: 4px;
}

.pricing-price .price {
    font-size: 40px;
    font-weight: 700;
    color: var(--color-text);
}

.pricing-price .period {
    font-size: 16px;
    color: var(--color-text-light);
}

.pricing-annual {
    font-size: 13px;
    color: var(--color-text-lighter);
    margin-bottom: 24px;
}

.pricing-features {
    text-align: left;
    margin-bottom: 24px;
}

.pricing-features li {
    font-size: 14px;
    color: var(--color-text-light);
    padding: 8px 0;
    padding-left: 24px;
    position: relative;
}

.pricing-features li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--color-primary);
    font-weight: 600;
}

.pricing-note {
    font-size: 12px;
    color: var(--color-text-lighter);
    margin-top: 12px;
}

.pricing-scale {
    text-align: center;
    padding: 48px;
    background: var(--color-bg-soft);
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
}

.pricing-scale h3 {
    font-size: 22px;
    font-weight: 600;
    margin-bottom: 12px;
}

.pricing-scale p {
    font-size: 16px;
    color: var(--color-text-light);
    margin-bottom: 24px;
}

/* === TESTIMONIAL === */
.testimonial {
    padding: 80px 0;
    background: var(--color-bg-soft);
}

.testimonial blockquote {
    max-width: 700px;
    margin: 0 auto;
    text-align: center;
}

.testimonial blockquote p {
    font-size: 24px;
    font-weight: 500;
    line-height: 1.5;
    color: var(--color-text);
    margin-bottom: 24px;
}

.testimonial cite {
    font-style: normal;
}

.testimonial cite strong {
    display: block;
    font-size: 16px;
    font-weight: 600;
    color: var(--color-text);
}

.testimonial cite span {
    font-size: 14px;
    color: var(--color-text-light);
}

/* === CTA === */
.cta {
    padding: 100px 0;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    text-align: center;
}

.cta h2 {
    font-size: 36px;
    font-weight: 700;
    color: white;
    margin-bottom: 16px;
}

.cta p {
    font-size: 18px;
    color: rgba(255, 255, 255, 0.85);
    margin-bottom: 32px;
}

.cta .btn-primary {
    background: white;
    color: var(--color-primary);
}

.cta .btn-primary:hover {
    background: var(--color-bg-soft);
}

/* === FOOTER === */
.footer {
    padding: 64px 0 32px;
    background: var(--color-text);
    color: white;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: 48px;
    margin-bottom: 48px;
}

.footer-brand .logo {
    color: white;
    margin-bottom: 16px;
}

.footer-brand p {
    font-size: 14px;
    color: rgba(255, 255, 255, 0.6);
    line-height: 1.6;
}

.footer-links h4 {
    font-size: 14px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 16px;
    color: rgba(255, 255, 255, 0.5);
}

.footer-links li {
    margin-bottom: 12px;
}

.footer-links a {
    font-size: 14px;
    color: rgba(255, 255, 255, 0.75);
    transition: color var(--transition);
}

.footer-links a:hover {
    color: white;
}

.footer-bottom {
    padding-top: 32px;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-bottom p {
    font-size: 13px;
    color: rgba(255, 255, 255, 0.4);
    text-align: center;
}

/* === RESPONSIVE === */
@media (max-width: 1024px) {
    .pricing-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .footer-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    .nav-links a:not(.btn) {
        display: none;
    }

    .hero {
        padding: 120px 0 60px;
    }

    .hero h1 {
        font-size: 36px;
    }

    .hero-subtitle {
        font-size: 17px;
    }

    .phone-mockup {
        width: 240px;
        height: 480px;
    }

    .feature-grid {
        grid-template-columns: 1fr;
    }

    .feature-card.featured {
        grid-column: span 1;
    }

    .pricing-grid {
        grid-template-columns: 1fr;
        max-width: 400px;
        margin: 0 auto 48px;
    }

    .footer-grid {
        grid-template-columns: 1fr;
        gap: 32px;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 16px;
    }

    .hero h1 {
        font-size: 32px;
    }

    .problem h2,
    .solution-header h2,
    .pricing-header h2,
    .cta h2 {
        font-size: 28px;
    }
}