:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --secondary-color: #0ea5e9;
    --accent-color: #f59e0b;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-light: #94a3b8;
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --bg-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.1);
    --shadow-lg: 0 10px 15px rgba(0,0,0,0.1);
    --shadow-xl: 0 20px 25px rgba(0,0,0,0.15);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: Inter, system-ui, sans-serif;
    color: var(--text-primary);
    background: linear-gradient(180deg, #fafbfc 0%, #f1f5f9 100%);
    line-height: 1.6;
    padding-top: 70px;
}

/* ================= HEADER ================= */

header {
    position: fixed;
    top: 0;
    width: 100%;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow-sm);
    z-index: 1000;
    transition: box-shadow 0.3s ease;
    border-bottom: 1px solid rgba(226, 232, 240, 0.6);
}

nav ul {
    display: flex;
    justify-content: center;
    list-style: none;
    padding: 20px;
    gap: 30px;
}

nav ul li {
    position: relative;
}

nav ul li::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 50%;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    transition: width 0.3s ease, left 0.3s ease;
}

nav ul li:hover::after {
    width: 100%;
    left: 0;
}

nav ul li a {
    text-decoration: none;
    color: var(--text-secondary);
    font-weight: 500;
    transition: color 0.3s ease;
}

nav ul li a:hover {
    color: var(--primary-color);
}

/* ================= HERO (HOME) ================= */

#short_intro {
    min-height: 80vh;
    background: var(--bg-gradient);
    color: white;
    text-align: center;
    padding: 120px 20px 80px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    position: relative;
}

#short_intro::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 120px;
    background: linear-gradient(to bottom, transparent, rgba(248, 250, 252, 0.3));
    pointer-events: none;
}

#short_intro h1 {
    font-size: 3.2rem;
    margin-bottom: 24px;
    font-weight: 700;
    letter-spacing: -0.02em;
    opacity: 0;
    animation: fadeInUp 0.8s ease forwards;
}

#short_intro h3 {
    font-size: 1.5rem;
    font-weight: 400;
    margin-bottom: 48px;
    opacity: 0.95;
    letter-spacing: 0.01em;
    animation: fadeInUp 0.8s ease 0.2s forwards;
}

#short_intro button {
    padding: 16px 44px;
    border-radius: 50px;
    border: none;
    font-size: 1rem;
    font-weight: 600;
    color: var(--primary-color);
    background: white;
    cursor: pointer;
    box-shadow: 0 8px 24px rgba(0,0,0,0.15);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    opacity: 0;
    animation: fadeInUp 0.8s ease 0.4s forwards;
}

#short_intro button:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 32px rgba(0,0,0,0.2);
}

#short_intro button:active {
    transform: translateY(-2px);
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ================= INTRO ================= */

#intro {
    padding: 120px 20px;
    background: linear-gradient(to bottom, #f8fafc, #ffffff);
    text-align: center;
}

#intro p {
    font-size: 1.25rem;
    color: var(--text-secondary);
    max-width: 700px;
    margin: 0 auto 20px;
    line-height: 1.8;
    transition: color 0.3s ease;
}

#intro p:hover {
    color: var(--text-primary);
}

/* ================= POPULAR SKILLS (HOME) ================= */

#popular_skills {
    padding: 120px 20px;
    text-align: center;
    background: #ffffff;
}

#popular_skills h2 {
    font-size: 2.5rem;
    margin-bottom: 16px;
    font-weight: 700;
    letter-spacing: -0.02em;
    color: var(--text-primary);
}

#popular_skills h2::after {
    content: '';
    display: block;
    width: 80px;
    height: 4px;
    background: var(--primary-color);
    margin: 24px auto 40px;
    border-radius: 2px;
}

#popular_skills button {
    margin: 10px;
    padding: 20px 30px;
    border-radius: 14px;
    border: 2px solid var(--border-color);
    background: #ffffff;
    font-weight: 600;
    cursor: pointer;
    color: var(--text-secondary);
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

#popular_skills button::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(99, 102, 241, 0.08), transparent);
    transition: left 0.5s ease;
}

#popular_skills button:hover::before {
    left: 100%;
}

#popular_skills button:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

#popular_skills button:active {
    transform: translateY(-2px);
}

/* ================= HOW IT WORKS ================= */

#how_it_works {
    padding: 120px 20px;
    background: linear-gradient(to bottom, #ffffff, #f8fafc);
}

#how_it_works h3 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 16px;
    font-weight: 700;
    letter-spacing: -0.02em;
    color: var(--text-primary);
}

#how_it_works h3::after {
    content: '';
    display: block;
    width: 80px;
    height: 4px;
    background: var(--primary-color);
    margin: 24px auto 56px;
    border-radius: 2px;
}

#how_it_works ol {
    max-width: 700px;
    margin: auto;
}

#how_it_works li {
    background: white;
    margin-bottom: 20px;
    padding: 24px 28px;
    border-radius: 14px;
    box-shadow: var(--shadow-sm);
    transition: all 0.3s ease;
    border-left: 4px solid transparent;
    font-size: 1.05rem;
    line-height: 1.7;
}

#how_it_works li:hover {
    transform: translateX(8px);
    box-shadow: var(--shadow-md);
    border-left-color: var(--primary-color);
}

/* ================= ROADMAP ================= */

#roadmap {
    padding: 120px 20px;
    text-align: center;
    background: #f8fafc;
}

#roadmap h2 {
    font-size: 2.5rem;
    margin-bottom: 16px;
    font-weight: 700;
    letter-spacing: -0.02em;
    color: var(--text-primary);
}

#roadmap h2::after {
    content: '';
    display: block;
    width: 80px;
    height: 4px;
    background: var(--primary-color);
    margin: 24px auto 56px;
    border-radius: 2px;
}

#roadmap ul {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px,1fr));
    gap: 20px;
    list-style: none;
    max-width: 900px;
    margin: 0 auto;
}

#roadmap li {
    background: white;
    padding: 28px;
    border-radius: 14px;
    font-weight: 500;
    transition: all 0.3s ease;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
}

#roadmap li:hover {
    border-color: var(--primary-light);
    transform: translateY(-6px);
    box-shadow: var(--shadow-lg);
}

/* ================= QUOTE ================= */

#quote {
    padding: 120px 20px;
    background: var(--bg-gradient);
    text-align: center;
    position: relative;
}

#quote::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 80px;
    background: linear-gradient(to bottom, rgba(248, 250, 252, 0.2), transparent);
    pointer-events: none;
}

#quote p {
    font-size: 2rem;
    font-style: italic;
    color: white;
    transition: transform 0.3s ease;
    font-weight: 400;
    line-height: 1.5;
    max-width: 800px;
    margin: 0 auto;
}

#quote p:hover {
    transform: scale(1.02);
}

/* ================= SKILLS PAGE ================= */

#skills_intro {
    padding: 120px 20px 80px;
    text-align: center;
    background: linear-gradient(to bottom, #fafbfc, #f8fafc);
}

#skills_intro h1 {
    font-size: 3rem;
    margin-bottom: 20px;
    font-weight: 700;
    letter-spacing: -0.02em;
    color: var(--text-primary);
}

#skills_intro h1::after {
    content: '';
    display: block;
    width: 100px;
    height: 4px;
    background: var(--primary-color);
    margin: 28px auto 0;
    border-radius: 2px;
}

#skills_intro p {
    font-size: 1.15rem;
    color: var(--text-secondary);
    max-width: 700px;
    margin: 24px auto 0;
    line-height: 1.7;
}

#skills_list {
    padding: 60px 20px 120px;
    max-width: 900px;
    margin: 0 auto;
    background: linear-gradient(to bottom, #f8fafc, #ffffff);
}

#skills_list ul {
    list-style: none;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 24px;
}

#skills_list li {
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 28px 32px;
    box-shadow: var(--shadow-sm);
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

#skills_list li::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 0;
    background: var(--primary-color);
    transition: height 0.3s ease;
}

#skills_list li:hover::before {
    height: 100%;
}

#skills_list li:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-light);
}

#skills_list li a {
    text-decoration: none;
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    transition: color 0.3s ease;
}

#skills_list li a:hover {
    color: var(--primary-color);
}

/* ================= ABOUT ME ================= */

#about-me {
    max-width: 900px;
    margin: 0 auto 100px;
    padding: 80px 40px;
    text-align: left;
    background: #ffffff;
    border-radius: 20px;
    box-shadow: 0 2px 12px rgba(0,0,0,0.04);
}

#about-me h2 {
    font-size: 2.5rem;
    color: var(--text-primary);
    margin-bottom: 12px;
    font-weight: 700;
    letter-spacing: -0.02em;
    position: relative;
    padding-bottom: 20px;
}

#about-me h2::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 80px;
    height: 4px;
    background: var(--primary-color);
    transition: width 0.3s ease;
    border-radius: 2px;
}

#about-me h2:hover::after {
    width: 140px;
}

#about-me p {
    font-size: 1.15rem;
    color: var(--text-secondary);
    line-height: 1.8;
    max-width: 100%;
    margin: 28px 0 16px 0;
    transition: color 0.3s ease;
}

#about-me p:hover {
    color: var(--text-primary);
}

/* ================= DSA PAGE ================= */

#skill-detail {
    max-width: 900px;
    margin: 60px auto 120px;
    padding: 60px 40px;
    background: #ffffff;
    border-radius: 20px;
    box-shadow: 0 2px 12px rgba(0,0,0,0.04);
}

#skill-detail h1 {
    text-align: center;
    margin-bottom: 16px;
    font-size: 3.2rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    color: var(--text-primary);
}

#skill-detail h1::after {
    content: '';
    display: block;
    width: 100px;
    height: 4px;
    background: var(--primary-color);
    margin: 28px auto 64px;
    border-radius: 2px;
}

#what-is-dsa,
#why-dsa,
#dsa-roadmap,
#dsa-resources {
    background: linear-gradient(to bottom, #fafbfc, #ffffff);
    padding: 44px;
    margin-bottom: 32px;
    border-radius: 16px;
    box-shadow: 0 1px 4px rgba(0,0,0,0.04);
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
}

#what-is-dsa:hover,
#why-dsa:hover,
#dsa-roadmap:hover,
#dsa-resources:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-4px);
    background: #ffffff;
}

#what-is-dsa h2,
#why-dsa h2,
#dsa-roadmap h2,
#dsa-resources h2 {
    color: var(--primary-dark);
    margin-bottom: 8px;
    font-size: 2rem;
    font-weight: 700;
    letter-spacing: -0.01em;
    border-bottom: 3px solid var(--primary-color);
    padding-bottom: 16px;
    transition: border-color 0.3s ease;
}

#what-is-dsa h2::after,
#why-dsa h2::after,
#dsa-roadmap h2::after,
#dsa-resources h2::after {
    content: '';
    display: block;
    margin-top: 20px;
}

#what-is-dsa p,
#why-dsa p,
#dsa-roadmap p,
#dsa-resources p {
    font-size: 1.08rem;
    line-height: 1.8;
    color: var(--text-secondary);
}

#dsa-roadmap ol {
    list-style-position: inside;
}

#dsa-roadmap li {
    margin-bottom: 16px;
    transition: all 0.3s ease;
    padding-left: 8px;
    border-left: 3px solid transparent;
    font-size: 1.08rem;
    line-height: 1.7;
}

#dsa-roadmap li:hover {
    padding-left: 16px;
    border-left-color: var(--primary-color);
    color: var(--text-primary);
}

/* ================= FOOTER ================= */

footer {
    background: var(--text-primary);
    color: white;
    padding: 48px 20px;
    border-top: 4px solid var(--primary-color);
}

footer ul {
    display: flex;
    justify-content: center;
    list-style: none;
    gap: 36px;
}

footer ul li a {
    color: var(--text-light);
    text-decoration: none;
    transition: all 0.3s ease;
    position: relative;
    font-weight: 500;
}

footer ul li a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 50%;
    width: 0;
    height: 2px;
    background: white;
    transition: width 0.3s ease, left 0.3s ease;
}

footer ul li a:hover::after {
    width: 100%;
    left: 0;
}

footer ul li a:hover {
    color: white;
}

#about-goal ul {
    list-style: none;
    padding-left: 0;
}

#about-goal li {
    font-size: 1.15rem;
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: 16px;
    padding-left: 28px;
    position: relative;
    transition: all 0.3s ease;
}

#about-goal li::before {
    content: "•";
    position: absolute;
    left: 0;
    color: var(--primary-color);
    font-size: 1.4rem;
    transition: transform 0.3s ease;
}

#about-goal li:hover {
    padding-left: 32px;
    color: var(--text-primary);
}

#about-goal li:hover::before {
    transform: scale(1.3);
}

/* ================= RESPONSIVE ADJUSTMENTS ================= */

@media (max-width: 768px) {
    #about-me,
    #skill-detail {
        padding: 60px 24px;
        margin-left: 20px;
        margin-right: 20px;
    }
}