:root {
    --blue: #1677b8;
    --blue-light: #eaf6fc;
    --blue-soft: #f5fbfe;
    --dark: #172b3a;
    --text: #526575;
    --white: #ffffff;
    --border: #e5eef4;
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    font-family:
        -apple-system,
        BlinkMacSystemFont,
        "SF Pro Display",
        "SF Pro Text",
        "Segoe UI",
        Roboto,
        Arial,
        sans-serif;
    color: var(--dark);
    background: var(--blue-soft);
}

/* --------------------------------
   Navigation
-------------------------------- */

.topbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: 64px;
    display: flex;
    align-items: center;
    padding: 0 22px;
    background: rgba(255, 255, 255, 0.88);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid rgba(220, 235, 243, 0.8);
    z-index: 1000;
}

.back-button {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    color: var(--blue);
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 600;
    transition: opacity 0.2s ease;
}

.back-button:hover {
    opacity: 0.7;
}

/* --------------------------------
   Container
-------------------------------- */

.container {
    width: min(100% - 32px, 900px);
    margin: 0 auto;
    padding: 110px 0 70px;
}

/* --------------------------------
   Hero
-------------------------------- */

.hero {
    text-align: center;
    margin-bottom: 55px;
}

.icon {
    width: 64px;
    height: 64px;
    margin: 0 auto 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.7rem;
    color: var(--blue);
    background: var(--blue-light);
    border-radius: 20px;
}

.hero h1 {
    margin: 0 0 15px;
    font-size: clamp(2.2rem, 6vw, 3.5rem);
    line-height: 1.05;
    letter-spacing: -0.045em;
    font-weight: 750;
}

.hero p {
    max-width: 650px;
    margin: 0 auto;
    color: var(--text);
    font-size: 1.08rem;
    line-height: 1.7;
}

/* --------------------------------
   Feature
-------------------------------- */

.feature {
    margin-bottom: 34px;
    background: var(--white);
    border: 1px solid var(--border);
    border-radius: 28px;
    overflow: hidden;
    box-shadow: 0 12px 40px rgba(31, 82, 112, 0.07);
}

.feature-content {
    padding: 34px;
}

.feature-number {
    display: inline-block;
    margin-bottom: 12px;
    font-size: 0.78rem;
    font-weight: 700;
    color: var(--blue);
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.feature h2 {
    margin: 0 0 15px;
    font-size: 1.55rem;
    letter-spacing: -0.025em;
}

.feature p {
    margin: 0 0 15px;
    color: var(--text);
    font-size: 1rem;
    line-height: 1.75;
}

.feature p:last-child {
    margin-bottom: 0;
}

/* --------------------------------
   Screenshots
-------------------------------- */

.screenshot {
    padding: 24px;
    background: linear-gradient(145deg, #edf7fc, #f8fcfe);
    text-align: center;
}

.screenshot img {
    display: block;
    width: 100%;
    max-width: 600px;
    height: auto;
    margin: auto;
    border-radius: 18px;
    box-shadow: 0 18px 45px rgba(25, 70, 95, 0.18);
}

.placeholder-screenshot {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 200px;
    margin: 0 auto;
    max-width: 600px;
    border-radius: 18px;
    border: 2px dashed rgba(22, 119, 184, 0.25);
    background: repeating-linear-gradient(
        -45deg,
        rgba(234, 246, 252, 0.6),
        rgba(234, 246, 252, 0.6) 10px,
        rgba(245, 251, 254, 0.8) 10px,
        rgba(245, 251, 254, 0.8) 20px
    );
    color: #8294a1;
    font-size: 0.95rem;
    font-weight: 500;
}

/* --------------------------------
   Highlight
-------------------------------- */

.highlight {
    margin-top: 22px;
    padding: 18px 20px;
    background: var(--blue-light);
    border-radius: 16px;
    color: #31586e;
    font-size: 0.95rem;
    line-height: 1.65;
}

.highlight strong {
    color: var(--blue);
}

/* --------------------------------
   Footer
-------------------------------- */

.footer {
    text-align: center;
    margin-top: 55px;
    color: #8294a1;
    font-size: 0.85rem;
}

/* --------------------------------
   Hub — modules grid
-------------------------------- */

.modules-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 18px;
}

.module-card {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
    padding: 24px 22px;
    background: var(--white);
    border: 1px solid var(--border);
    border-radius: 22px;
    text-decoration: none;
    color: var(--dark);
    box-shadow: 0 12px 40px rgba(31, 82, 112, 0.07);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.module-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 16px 48px rgba(31, 82, 112, 0.12);
}

.module-card-icon {
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.3rem;
    color: var(--blue);
    background: var(--blue-light);
    border-radius: 14px;
}

.module-card-title {
    margin: 0;
    font-size: 1.1rem;
    font-weight: 650;
    letter-spacing: -0.02em;
}

.module-card-subtitle {
    margin: 0;
    color: var(--text);
    font-size: 0.88rem;
    line-height: 1.5;
}

/* --------------------------------
   Mobile
-------------------------------- */

@media (max-width: 600px) {
    .topbar {
        height: 58px;
        padding: 0 16px;
    }

    .container {
        width: min(100% - 24px, 900px);
        padding-top: 90px;
    }

    .hero {
        margin-bottom: 35px;
    }

    .hero h1 {
        font-size: 2.25rem;
    }

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

    .feature {
        border-radius: 22px;
    }

    .feature-content {
        padding: 24px 20px;
    }

    .screenshot {
        padding: 14px;
    }

    .screenshot img {
        border-radius: 13px;
    }

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