:root {
    --bg-color: #ffffff;
    --text-primary: #1d1d1f;
    --text-secondary: #86868b;
    --accent-blue: #0071e3;
    --nav-bg: rgba(255, 255, 255, 0.8);
    --border-color: rgba(0, 0, 0, 0.08);
    --font-stack: "SF Pro Display", "SF Pro Icons", "Helvetica Neue", "Helvetica", "Arial", sans-serif;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }

    to {
        opacity: 1;
    }
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    -webkit-font-smoothing: antialiased;
}

body {
    font-family: var(--font-stack);
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.47059;
    font-weight: 400;
    overflow-x: hidden;
}

header {
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
    height: 52px;
    background-color: var(--nav-bg);
    backdrop-filter: saturate(180%) blur(20px);
    -webkit-backdrop-filter: saturate(180%) blur(20px);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: center;
    padding: 0 20px;
    animation: fadeIn 1s ease-out;
}

nav ul {
    display: flex;
    gap: 34px;
    align-items: center;
    height: 100%;
}

nav a {
    font-size: 13px;
    color: var(--text-primary);
    opacity: 0.8;
    text-decoration: none;
    transition: opacity 0.3s ease, color 0.3s ease;
}

nav a:hover {
    opacity: 1;
    color: var(--accent-blue);
}

.container {
    max-width: 980px;
    margin: 0 auto;
    padding: 120px 22px 100px;
    animation: fadeInUp 1s cubic-bezier(0.2, 0.8, 0.2, 1);
}

.hero {
    text-align: center;
    padding: 60px 0 100px;
}

.section-tag {
    font-size: 21px;
    font-weight: 600;
    color: var(--accent-blue);
    display: block;
    margin-bottom: 20px;
    letter-spacing: 0.011em;
}

.hero h1 {
    font-size: 72px;
    line-height: 1.05;
    font-weight: 700;
    letter-spacing: -0.015em;
    margin-bottom: 24px;
}

.hero p {
    font-size: 28px;
    line-height: 1.14;
    font-weight: 600;
    color: var(--text-secondary);
    max-width: 800px;
    margin: 0 auto;
}

/* Linear Content Sections - Removed "Boxes" */
section {
    margin-bottom: 140px;
    opacity: 0;
    animation: fadeInUp 1s cubic-bezier(0.2, 0.8, 0.2, 1) forwards;
}

section:nth-child(2) {
    animation-delay: 0.2s;
}

section:nth-child(3) {
    animation-delay: 0.4s;
}

section:nth-child(4) {
    animation-delay: 0.6s;
}

h2 {
    font-size: 48px;
    line-height: 1.08;
    font-weight: 700;
    margin-bottom: 40px;
    letter-spacing: -0.003em;
}

.content-block {
    font-size: 24px;
    line-height: 1.33;
    font-weight: 400;
    color: var(--text-primary);
    padding-bottom: 50px;
    border-bottom: 1px solid var(--border-color);
}

/* Linear Table of Contents */
.toc-list {
    display: flex;
    flex-direction: column;
}

.toc-row {
    display: grid;
    grid-template-columns: 80px 1fr 200px;
    padding: 30px 0;
    border-bottom: 1px solid var(--border-color);
    align-items: center;
    transition: background-color 0.3s ease;
    cursor: default;
}

.toc-row:hover {
    background-color: rgba(0, 0, 0, 0.01);
}

.toc-number {
    font-size: 17px;
    font-weight: 600;
    color: var(--text-secondary);
}

.toc-title {
    font-size: 24px;
    font-weight: 600;
    color: var(--text-primary);
}

.toc-description {
    font-size: 14px;
    color: var(--text-secondary);
    text-align: right;
}

/* Specific Page Elements */
.mentor-profile {
    display: flex;
    gap: 60px;
    align-items: flex-start;
    padding-top: 40px;
}

.mentor-image-placeholder {
    width: 320px;
    height: 400px;
    background: #f5f5f7;
    border-radius: 18px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform 0.5s ease;
}

.mentor-image-placeholder:hover {
    transform: scale(1.02);
}

.doc-container {
    width: 100%;
    height: 800px;
    border-radius: 20px;
    overflow: hidden;
    border: 1px solid var(--border-color);
    margin-top: 40px;
    transition: box-shadow 0.3s ease;
}

.doc-container:hover {
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.05);
}

.doc-container iframe {
    width: 100%;
    height: 100%;
    border: none;
}

footer {
    padding: 80px 22px;
    max-width: 980px;
    margin: 0 auto;
    border-top: 1px solid var(--border-color);
}

footer p {
    font-size: 12px;
    color: var(--text-secondary);
    margin-bottom: 10px;
}

@media (max-width: 734px) {
    .hero h1 {
        font-size: 48px;
    }

    .hero p {
        font-size: 21px;
    }

    h2 {
        font-size: 32px;
    }

    .toc-row {
        grid-template-columns: 40px 1fr;
    }

    .toc-description {
        display: none;
    }

    .mentor-profile {
        flex-direction: column;
    }

    nav ul {
        gap: 15px;
    }

    nav a {
        font-size: 11px;
    }
}