:root {
    --orange: #FF6B35;
    --orange-dark: #E85A2A;
    --navy: #0A192F;
    --navy-light: #112240;
}

* { box-sizing: border-box; }
body { font-family: 'Outfit', sans-serif; background: #F8F7F4; color: var(--navy); }
h1, h2, h3, h4, .logo { font-family: 'Outfit', sans-serif; }

/* NAV */
nav {
    position: sticky; top: 0; z-index: 100;
    display: flex; justify-content: space-between; align-items: center;
    padding: 1.2rem 2.5rem;
    background: rgba(248,247,244,0.85);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid rgba(0,0,0,0.06);
    gap: 2rem;
}
.logo { font-size: 1.5rem; font-weight: 800; letter-spacing: -0.04em; color: var(--navy); flex-shrink: 0; }
.logo span { color: var(--orange); }
.nav-links { display: flex; gap: 2rem; align-items: center; font-size: 0.9rem; font-weight: 500; }
.nav-links a { color: var(--navy); text-decoration: none; opacity: 0.7; transition: opacity 0.2s; }
.nav-links a:hover { opacity: 1; }
.nav-cta {
    background: var(--orange); color: #fff !important; opacity: 1 !important;
    padding: 0.55rem 1.2rem; border-radius: 100px;
    font-size: 0.85rem; font-weight: 600;
    text-decoration: none;
}

/* HAMBURGER */
.hamburger {
    display: none; flex-direction: column; justify-content: center; gap: 5px;
    cursor: pointer; padding: 4px; background: none; border: none;
    flex-shrink: 0;
}
.hamburger span {
    display: block; width: 22px; height: 2px;
    background: var(--navy); border-radius: 2px;
    transition: transform 0.3s, opacity 0.3s;
}
.hamburger.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.hamburger.open span:nth-child(2) { opacity: 0; }
.hamburger.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* MOBILE MENU */
.mobile-menu {
    position: absolute; top: 100%; left: 0; right: 0;
    background: rgba(248,247,244,0.98);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid rgba(0,0,0,0.08);
    overflow: hidden;
    max-height: 0;
    transition: max-height 0.35s cubic-bezier(0.4,0,0.2,1), padding 0.35s;
    padding: 0 1.5rem;
}
.mobile-menu.open {
    max-height: 300px;
    padding: 0.75rem 1.5rem 1.25rem;
}
.mobile-menu a {
    display: block;
    color: var(--navy); text-decoration: none;
    font-size: 1rem; font-weight: 500;
    padding: 0.75rem 0;
    border-bottom: 1px solid rgba(0,0,0,0.06);
    opacity: 0.75;
}
.mobile-menu a:last-child { border-bottom: none; }
.mobile-menu .nav-cta {
    margin-top: 0.75rem;
    text-align: center;
    border-radius: 12px;
    padding: 0.75rem;
    border-bottom: none;
    opacity: 1;
}

@media (max-width: 640px) {
    nav { padding: 1rem 1.5rem; }
    .nav-links { display: none; }
    .hamburger { display: flex; }
}

/* HERO */
.hero {
    background: var(--navy);
    color: white;
    padding: 7rem 2rem 6rem;
    text-align: center;
    position: relative;
    overflow: hidden;
}
.hero::before {
    content: '';
    position: absolute; inset: 0;
    background: radial-gradient(ellipse 80% 60% at 50% 0%, rgba(255,107,53,0.15) 0%, transparent 70%);
    pointer-events: none;
}
.hero-badge {
    display: inline-block;
    background: rgba(255,107,53,0.15);
    border: 1px solid rgba(255,107,53,0.4);
    color: var(--orange);
    font-size: 0.75rem; font-weight: 700; letter-spacing: 0.15em;
    text-transform: uppercase;
    padding: 0.4rem 1rem; border-radius: 100px;
    margin-bottom: 2rem;
}
.hero h1 {
    font-size: clamp(3rem, 8vw, 6rem);
    font-weight: 800;
    line-height: 1.0;
    letter-spacing: -0.03em;
    margin-bottom: 1.5rem;
}
.hero h1 em { color: var(--orange); font-style: normal; }
.hero p {
    color: rgba(255,255,255,0.55);
    font-size: 1.15rem; max-width: 520px; margin: 0 auto 2.5rem;
    line-height: 1.7;
}
.hero-buttons { display: flex; gap: 1rem; justify-content: center; flex-wrap: wrap; }
.btn-primary {
    background: var(--orange); color: #fff;
    font-family: 'Outfit', sans-serif;
    font-weight: 700; font-size: 1rem;
    padding: 1rem 2rem; border-radius: 14px;
    border: none; cursor: pointer;
    transition: transform 0.2s, background 0.2s;
    text-decoration: none;
}
.btn-primary:hover { transform: scale(1.04); background: var(--orange-dark); }
.btn-secondary {
    background: transparent; color: #fff;
    font-family: 'Outfit', sans-serif;
    font-weight: 700; font-size: 1rem;
    padding: 1rem 2rem; border-radius: 14px;
    border: 1px solid rgba(255,255,255,0.2); cursor: pointer;
    transition: background 0.2s, border-color 0.2s;
    text-decoration: none;
}
.btn-secondary:hover { background: rgba(255,255,255,0.08); border-color: rgba(255,255,255,0.4); }

/* CARDS */
.cards-section {
    padding: 6rem 2rem;
    max-width: 1100px; margin: 0 auto;
}
.cards-section h2 {
    text-align: center;
    font-size: 2rem; font-weight: 800; letter-spacing: -0.03em;
    margin-bottom: 3rem;
}
.cards-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 1.5rem; }
.card {
    background: white;
    border: 1px solid rgba(0,0,0,0.07);
    border-radius: 20px;
    padding: 2.2rem;
    transition: transform 0.25s, box-shadow 0.25s;
}
.card:hover { transform: translateY(-4px); box-shadow: 0 16px 40px rgba(0,0,0,0.09); }
.card-icon { font-size: 2rem; margin-bottom: 1.2rem; }
.card h3 { font-size: 1.2rem; font-weight: 800; margin-bottom: 0.6rem; letter-spacing: -0.02em; }
.card p { color: #6B7280; line-height: 1.65; font-size: 0.95rem; }
.card-tag {
    display: inline-block; margin-top: 1.2rem;
    background: #F3F4F6; color: #374151;
    font-size: 0.75rem; font-weight: 600;
    padding: 0.3rem 0.8rem; border-radius: 100px;
}

/* PRICING */
.pricing-section {
    background: var(--navy);
    color: white;
    padding: 6rem 2rem;
}
.pricing-inner { max-width: 1000px; margin: 0 auto; }
.pricing-section h2 {
    text-align: center;
    font-size: 2.2rem; font-weight: 800; letter-spacing: -0.03em;
    margin-bottom: 0.75rem;
}
.pricing-section .subtitle {
    text-align: center; color: rgba(255,255,255,0.45);
    margin-bottom: 3.5rem; font-size: 1rem;
}
.pricing-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 1.5rem; }
.plan {
    background: rgba(255,255,255,0.05);
    border: 1px solid rgba(255,255,255,0.1);
    border-radius: 20px; padding: 2.2rem;
    transition: border-color 0.2s;
}
.plan:hover { border-color: rgba(255,107,53,0.4); }
.plan.featured {
    background: var(--orange);
    border-color: var(--orange);
}
.plan-name { font-family: 'Syne', sans-serif; font-size: 0.85rem; font-weight: 700; letter-spacing: 0.1em; text-transform: uppercase; opacity: 0.7; margin-bottom: 1rem; }
.plan.featured .plan-name { opacity: 0.85; }
.plan-price { font-family: 'Syne', sans-serif; font-size: 3rem; font-weight: 800; letter-spacing: -0.04em; line-height: 1; margin-bottom: 0.3rem; }
.plan-period { font-size: 0.85rem; opacity: 0.5; margin-bottom: 1.5rem; }
.plan-divider { border: none; border-top: 1px solid rgba(255,255,255,0.1); margin: 1.5rem 0; }
.plan.featured .plan-divider { border-color: rgba(255,255,255,0.25); }
.plan-features { list-style: none; padding: 0; margin: 0 0 2rem; display: flex; flex-direction: column; gap: 0.75rem; }
.plan-features li { font-size: 0.92rem; display: flex; align-items: center; gap: 0.6rem; opacity: 0.85; }
.plan-features li::before { content: '✓'; font-weight: 700; flex-shrink: 0; }
.plan-btn {
    width: 100%; padding: 0.9rem;
    border-radius: 12px; border: none; cursor: pointer;
    font-family: 'Syne', sans-serif; font-weight: 700; font-size: 0.95rem;
    transition: transform 0.2s, opacity 0.2s;
}
.plan-btn:hover { transform: scale(1.03); }
.plan .plan-btn { background: rgba(255,255,255,0.1); color: white; }
.plan .plan-btn:hover { background: rgba(255,255,255,0.18); }
.plan.featured .plan-btn { background: var(--navy); color: white; }

/* FOOTER */
footer {
    padding: 3rem 2rem;
    text-align: center;
    border-top: 1px solid rgba(0,0,0,0.08);
    color: #9CA3AF; font-size: 0.85rem;
}
footer strong { color: var(--navy); }
footer a { color: var(--orange); text-decoration: none; }
footer a:hover { text-decoration: underline; }

/* ANIMATIONS */
@keyframes fadeUp {
    from { opacity: 0; transform: translateY(24px); }
    to { opacity: 1; transform: translateY(0); }
}
.hero-badge { animation: fadeUp 0.5s ease both; }
.hero h1 { animation: fadeUp 0.5s 0.1s ease both; }
.hero p { animation: fadeUp 0.5s 0.2s ease both; }
.hero-buttons { animation: fadeUp 0.5s 0.3s ease both; }

/* ARCHIVE PAGE */
.archive-container {
    max-width: 1000px; margin: 4rem auto; padding: 0 2rem;
}
.archive-header {
    text-align: center; margin-bottom: 3rem;
}
.archive-header h1 {
    font-size: 2.5rem; font-weight: 800; letter-spacing: -0.03em; margin-bottom: 1rem;
}
.archive-header p {
    color: #6B7280; font-size: 1.1rem; max-width: 600px; margin: 0 auto; line-height: 1.6;
}

/* TABS */
.exam-tabs {
    display: flex; justify-content: center; gap: 1rem; margin-bottom: 3rem;
    border-bottom: 2px solid rgba(0,0,0,0.05); padding-bottom: 1rem; flex-wrap: wrap;
}
.tab-btn {
    background: transparent; border: none; font-family: 'Outfit', sans-serif;
    font-size: 1.1rem; font-weight: 600; color: var(--navy); opacity: 0.6;
    cursor: pointer; padding: 0.5rem 1rem; transition: opacity 0.2s, color 0.2s;
    position: relative;
}
.tab-btn:hover { opacity: 1; }
.tab-btn.active { opacity: 1; color: var(--orange); }
.tab-btn.active::after {
    content: ''; position: absolute; bottom: -1.2rem; left: 0; right: 0;
    height: 3px; background: var(--orange); border-radius: 3px 3px 0 0;
}

/* CONTENT */
.exam-content { display: none; animation: fadeUp 0.3s ease; }
.exam-content.active { display: block; }
.exam-content h2 {
    font-size: 1.5rem; font-weight: 700; margin-bottom: 1.5rem; letter-spacing: -0.02em;
}

/* YEAR GRID */
.year-grid {
    display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 1rem;
}
.year-card {
    background: white; border: 1px solid rgba(0,0,0,0.08); border-radius: 12px;
    padding: 1.5rem; text-decoration: none; color: var(--navy);
    display: flex; flex-direction: column; align-items: flex-start; gap: 0.5rem;
    transition: transform 0.2s, box-shadow 0.2s, border-color 0.2s;
}
.year-card:hover {
    transform: translateY(-3px); box-shadow: 0 10px 20px rgba(0,0,0,0.05);
    border-color: rgba(255,107,53,0.3);
}
.year-title { font-weight: 700; font-size: 1.2rem; }
.problem-count { font-size: 0.85rem; color: #6B7280; font-weight: 500; }
.year-card.secondary {
    background: #F8F7F4; border-color: rgba(0,0,0,0.05); padding: 1rem 1.5rem;
}
.year-card.secondary:hover { background: white; border-color: rgba(0,0,0,0.1); }

/* EXAM DETAIL PAGE */
.exam-detail-container {
    max-width: 1000px; margin: 3rem auto; padding: 0 2rem;
}
.breadcrumb {
    font-size: 0.9rem; color: #6B7280; margin-bottom: 2rem; font-weight: 500;
}
.breadcrumb a { color: var(--orange); text-decoration: none; }
.breadcrumb a:hover { text-decoration: underline; }
.breadcrumb span { color: var(--navy); font-weight: 700; }

.exam-header {
    margin-bottom: 3rem; padding-bottom: 2rem; border-bottom: 1px solid rgba(0,0,0,0.08);
}
.exam-header h1 {
    font-size: 2.2rem; font-weight: 800; letter-spacing: -0.03em; margin-bottom: 0.5rem;
}
.exam-header p {
    color: #6B7280; font-size: 1.1rem;
}

.problem-list-section {
    margin-bottom: 4rem;
}
.problem-grid {
    display: grid; grid-template-columns: repeat(auto-fill, minmax(140px, 1fr)); gap: 1rem;
}
.problem-box {
    background: white; border: 1px solid rgba(0,0,0,0.08); border-radius: 12px;
    padding: 1.5rem 1rem; text-align: center; text-decoration: none;
    display: flex; flex-direction: column; align-items: center; gap: 0.5rem;
    transition: transform 0.2s, box-shadow 0.2s, border-color 0.2s;
}
.problem-box:hover {
    transform: translateY(-3px); box-shadow: 0 8px 20px rgba(0,0,0,0.06);
    border-color: rgba(255,107,53,0.4);
}
.problem-number {
    background: #F3F4F6; color: var(--navy); width: 40px; height: 40px;
    display: flex; align-items: center; justify-content: center;
    border-radius: 50%; font-weight: 800; font-size: 1.2rem;
    transition: background 0.2s, color 0.2s;
}
.problem-box:hover .problem-number {
    background: var(--orange); color: white;
}
.problem-text {
    font-size: 0.9rem; font-weight: 600; color: #6B7280;
}
.problem-box:hover .problem-text {
    color: var(--navy);
}

.answer-key-section {
    background: #F8F7F4; border: 1px solid rgba(0,0,0,0.05); border-radius: 16px;
    padding: 2rem; margin-bottom: 4rem; text-align: center;
}
.answer-key-section h2 {
    font-size: 1.5rem; font-weight: 700; margin-bottom: 1.5rem;
}
.answer-key-content {
    margin-top: 2rem; text-align: left;
}
.answer-list {
    display: grid; grid-template-columns: repeat(auto-fill, minmax(60px, 1fr));
    gap: 1rem; list-style-position: inside; font-weight: 700; font-size: 1.1rem;
    color: var(--navy); background: white; padding: 2rem; border-radius: 12px;
    border: 1px solid rgba(0,0,0,0.05);
}
.answer-list li::marker { color: #9CA3AF; font-weight: 500; }

/* PROBLEM SOLVE PAGE */
.problem-solve-container {
    max-width: 800px; margin: 3rem auto; padding: 0 2rem;
}
.problem-nav {
    display: flex; justify-content: space-between; align-items: center;
    margin-bottom: 2rem; padding-bottom: 1.5rem; border-bottom: 1px solid rgba(0,0,0,0.08);
}
.problem-nav h2 { font-size: 1.8rem; font-weight: 800; }
.nav-btn {
    padding: 0.5rem 1rem; border-radius: 8px; background: #F3F4F6;
    color: var(--navy); text-decoration: none; font-weight: 600; font-size: 0.9rem;
    transition: background 0.2s;
}
.nav-btn:hover { background: #E5E7EB; }
.nav-btn.disabled { opacity: 0.4; pointer-events: none; }

.question-section {
    background: white; border: 1px solid rgba(0,0,0,0.08); border-radius: 16px;
    padding: 2.5rem; font-size: 1.15rem; line-height: 1.6; margin-bottom: 2rem;
    box-shadow: 0 4px 12px rgba(0,0,0,0.03);
}
.options {
    display: flex; flex-direction: column; gap: 1rem; margin: 2rem 0;
}
.option-label {
    display: flex; align-items: center; gap: 1rem; padding: 1rem;
    border: 1px solid rgba(0,0,0,0.1); border-radius: 8px; cursor: pointer;
    transition: background 0.2s, border-color 0.2s;
}
.option-label:hover { background: #F8F7F4; border-color: var(--orange); }
.option-label input { width: 1.2rem; height: 1.2rem; accent-color: var(--orange); }
.option-label span { font-weight: 700; color: var(--orange); }

.feedback-msg {
    margin-top: 1.5rem; padding: 1rem; border-radius: 8px; font-weight: 600; display: none;
    animation: fadeUp 0.3s ease;
}
.feedback-msg.success { background: #D1FAE5; color: #065F46; border: 1px solid #10B981; }
.feedback-msg.error { background: #FEE2E2; color: #991B1B; border: 1px solid #EF4444; }

.solution-section {
    background: #F8F7F4; border: 1px solid rgba(0,0,0,0.08); border-radius: 16px;
    padding: 2.5rem; display: none; /* hidden until answered */
}
.solution-section.visible {
    display: block; animation: fadeUp 0.5s ease;
}
.solution-header {
    display: flex; justify-content: space-between; align-items: center;
    margin-bottom: 2rem; border-bottom: 2px solid rgba(0,0,0,0.05); padding-bottom: 1rem;
}
.solution-header h3 { font-size: 1.5rem; font-weight: 800; color: var(--navy); }
.difficulty-badge {
    background: #DBEAFE; color: #1E40AF; padding: 0.3rem 0.8rem;
    border-radius: 100px; font-size: 0.8rem; font-weight: 700;
}
.solution-step { margin-bottom: 1.5rem; line-height: 1.6; }
.solution-step h4 { font-size: 1.1rem; color: var(--orange); margin-bottom: 0.5rem; }
.final-answer {
    margin-top: 2rem; padding: 1.5rem; background: white; border: 8px;
    border: 2px dashed var(--orange); font-weight: 700; font-size: 1.2rem; text-align: center;
}

/* IMAGE PLACEHOLDERS */
.problem-image-placeholder {
    margin: 2rem 0;
    display: flex;
    justify-content: center;
}
.placeholder-box {
    width: 100%;
    max-width: 400px;
    height: 200px;
    background: #E5E7EB;
    border: 2px dashed #9CA3AF;
    border-radius: 12px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    color: #6B7280;
}
.placeholder-box p {
    font-weight: 700;
    margin-bottom: 0.5rem;
}
.placeholder-box span {
    font-size: 0.8rem;
}