/* Общи стилове за „Уроци по Авиация“ (uroci-aviaciya/*.html)
   Зарежда се след main.css. Старите уроци имат и собствени inline стилове – те остават с приоритет. */

:root {
    --primary: #3CB4E5;
    --primary-dark: #2898c8;
    --primary-light: #5FC8F0;
    --primary-lighter: #E8F4F8;
    --accent: #f5a623;
    --accent-dark: #d68f1d;
    --gray-50: #f9fafb;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-300: #d1d5db;
    --gray-500: #6b7280;
    --gray-600: #4b5563;
    --gray-700: #374151;
    --gray-900: #111827;
    --white: #ffffff;
    --success: #10b981;
    --error: #ef4444;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-full: 9999px;
    --spacing-xs: 0.5rem;
    --spacing-sm: 0.75rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    --transition-base: 0.3s ease;
}

body { font-family: 'Inter', sans-serif; line-height: 1.7; color: var(--gray-700); background: var(--gray-50); margin: 0; padding: 0; }

.lesson-container { max-width: 1000px; margin: 0 auto; padding: var(--spacing-xl) var(--spacing-md); }
.lesson-header {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    padding: var(--spacing-2xl) var(--spacing-xl);
    border-radius: var(--radius-xl);
    margin-bottom: var(--spacing-xl);
    box-shadow: 0 8px 30px rgba(60, 180, 229, 0.3);
}
.lesson-header h1 { font-size: clamp(1.8rem, 4vw, 2.5rem); font-weight: 800; margin: 0 0 var(--spacing-md) 0; line-height: 1.2; }
.lesson-header p { font-size: 1.15rem; opacity: 0.95; margin: 0; line-height: 1.6; }
.lesson-card {
    background: var(--white);
    padding: var(--spacing-2xl);
    border-radius: var(--radius-xl);
    box-shadow: 0 4px 20px rgba(0,0,0,0.08);
    margin-bottom: var(--spacing-xl);
}
.lesson-card h2 { color: var(--primary-dark); font-size: 1.75rem; font-weight: 700; margin-top: var(--spacing-2xl); margin-bottom: var(--spacing-lg); padding-bottom: var(--spacing-sm); border-bottom: 3px solid var(--primary-lighter); scroll-margin-top: 110px; }
.lesson-card h3 { color: var(--gray-900); font-size: 1.3rem; font-weight: 600; margin-top: var(--spacing-xl); margin-bottom: var(--spacing-md); }
.lesson-card p { margin-bottom: var(--spacing-md); line-height: 1.8; }
.lesson-card ul.plain { padding-left: var(--spacing-xl); line-height: 1.9; }

.lead { font-size: 1.15rem; color: var(--gray-900); }

.key-points {
    background: var(--primary-lighter);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    margin: var(--spacing-xl) 0;
    border-left: 5px solid var(--primary);
}
.key-points ul, .key-points ol { margin: var(--spacing-sm) 0 0; padding-left: var(--spacing-xl); }
.key-points li { margin-bottom: var(--spacing-sm); line-height: 1.8; }
.example-box {
    background: linear-gradient(135deg, #fff8e5 0%, #fff4e5 100%);
    border-left: 5px solid var(--accent);
    padding: var(--spacing-lg);
    margin: var(--spacing-xl) 0;
    border-radius: var(--radius-md);
}
.warning-box {
    background: linear-gradient(135deg, #fef2f2 0%, #fee2e2 100%);
    border-left: 5px solid var(--error);
    padding: var(--spacing-lg);
    margin: var(--spacing-xl) 0;
    border-radius: var(--radius-md);
}
.warning-box strong { color: #b91c1c; }
.formula {
    background: var(--gray-900);
    color: #e0f2fe;
    font-family: 'SF Mono', Menlo, Consolas, monospace;
    padding: var(--spacing-md) var(--spacing-lg);
    border-radius: var(--radius-md);
    margin: var(--spacing-lg) 0;
    font-size: 1.05rem;
    overflow-x: auto;
}
.lesson-card table { width: 100%; border-collapse: collapse; margin: var(--spacing-lg) 0; font-size: 0.97rem; }
.lesson-card th, .lesson-card td { padding: var(--spacing-sm) var(--spacing-md); text-align: left; border: 1px solid var(--gray-200); vertical-align: top; }
.lesson-card th { background: var(--primary-lighter); color: var(--primary-dark); font-weight: 600; }
.table-wrap { overflow-x: auto; -webkit-overflow-scrolling: touch; }

.lesson-figure { margin: var(--spacing-xl) 0; text-align: center; }
.lesson-figure img, .lesson-figure svg, .lesson-img { max-width: 100%; height: auto; border-radius: var(--radius-lg); }
.lesson-figure svg { background: var(--white); border: 1px solid var(--gray-200); }
.lesson-figure figcaption { color: var(--gray-600); font-size: 0.95rem; margin-top: var(--spacing-sm); }
.faa-figure img { display: block; margin: 0 auto; }
.lesson-figure .figure-credit { display: block; font-size: 0.78rem; color: var(--gray-500); margin-top: 0.25rem; }
.lesson-figure .figure-credit a { color: inherit; text-decoration: underline dotted; }

.back-link {
    display: inline-flex; align-items: center; gap: var(--spacing-sm);
    color: var(--primary); text-decoration: none; font-weight: 600;
    margin-bottom: var(--spacing-xl); transition: all var(--transition-base);
}
.back-link:hover { color: var(--primary-dark); transform: translateX(-5px); }

/* ---------- Мета ред под заглавието ---------- */
.lesson-meta {
    display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: var(--spacing-lg);
}
.lesson-meta span {
    background: rgba(255,255,255,0.2);
    border: 1px solid rgba(255,255,255,0.35);
    padding: 0.2rem 0.75rem;
    border-radius: var(--radius-full);
    font-size: 0.88rem;
    font-weight: 600;
}

/* ---------- Прогрес бар при четене ---------- */
.reading-progress {
    position: fixed; top: 0; left: 0; height: 4px; width: 0;
    background: linear-gradient(90deg, var(--primary), var(--accent));
    z-index: 10000; transition: width 0.1s linear;
}

/* ---------- Съдържание (TOC) ---------- */
.lesson-toc {
    background: var(--white);
    border: 1px solid var(--gray-200);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md) var(--spacing-lg);
    margin: 0 0 var(--spacing-xl);
}
.lesson-toc summary { cursor: pointer; font-weight: 700; color: var(--gray-900); }
.lesson-toc ol { margin: var(--spacing-sm) 0 0; padding-left: var(--spacing-lg); columns: 2; column-gap: var(--spacing-xl); }
.lesson-toc li { margin-bottom: 0.35rem; break-inside: avoid; }
.lesson-toc a { color: var(--primary-dark); text-decoration: none; }
.lesson-toc a:hover { text-decoration: underline; }

/* ---------- Калкулатори / интерактивни блокове ---------- */
.calc-box {
    background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
    border: 2px solid var(--primary-light);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    margin: var(--spacing-xl) 0;
}
.calc-box h3 { margin-top: 0; color: var(--primary-dark); }
.calc-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(190px, 1fr)); gap: var(--spacing-md); }
.calc-field label { display: block; font-weight: 600; font-size: 0.92rem; color: var(--gray-700); margin-bottom: 0.3rem; }
.calc-field input, .calc-field select, .calc-field textarea {
    width: 100%; box-sizing: border-box;
    padding: 0.6rem 0.75rem; border: 2px solid var(--gray-200); border-radius: var(--radius-md);
    font-size: 1rem; font-family: inherit; background: var(--white);
}
.calc-field input[type="range"] { padding: 0; border: none; background: transparent; accent-color: var(--primary-dark); }
.calc-field input:focus, .calc-field select:focus, .calc-field textarea:focus { outline: none; border-color: var(--primary); }
.calc-field .range-value { font-weight: 700; color: var(--primary-dark); }
.calc-result {
    margin-top: var(--spacing-lg);
    background: var(--white);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    border-left: 5px solid var(--primary);
}
.calc-result .big { font-size: 1.6rem; font-weight: 800; color: var(--primary-dark); }
.result-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: var(--spacing-md); }
.result-grid div { background: var(--gray-50); border-radius: var(--radius-md); padding: var(--spacing-sm) var(--spacing-md); }
.result-grid small { display: block; color: var(--gray-500); font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.03em; }
.result-grid b { font-size: 1.25rem; color: var(--gray-900); }
.calc-btn {
    background: var(--primary); color: white; border: none;
    padding: 0.6rem 1.2rem; border-radius: var(--radius-md);
    font-weight: 600; font-size: 0.95rem; cursor: pointer; font-family: inherit;
    transition: background var(--transition-base);
}
.calc-btn:hover { background: var(--primary-dark); }
.calc-btn.secondary { background: var(--white); color: var(--primary-dark); border: 2px solid var(--primary-light); }
.chip-row { display: flex; flex-wrap: wrap; gap: 0.5rem; margin: var(--spacing-sm) 0; }
.risk { display: inline-block; padding: 0.3rem 0.9rem; border-radius: var(--radius-full); font-weight: 700; color: #fff; }
.risk.low { background: var(--success); }
.risk.mod { background: var(--accent-dark); }
.risk.high { background: var(--error); }

/* ---------- Тест ---------- */
.quiz-section {
    background: linear-gradient(135deg, var(--white) 0%, var(--gray-50) 100%);
    border: 2px solid var(--primary);
    padding: var(--spacing-xl);
    border-radius: var(--radius-xl);
    margin-top: var(--spacing-2xl);
    box-shadow: 0 4px 20px rgba(60, 180, 229, 0.15);
}
.quiz-section h2 { margin-top: 0; color: var(--primary-dark); }
.quiz-question {
    background: var(--white);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    margin-bottom: var(--spacing-lg);
    border-left: 4px solid var(--primary);
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
    transition: border-color var(--transition-base);
}
.quiz-question > strong:first-child { color: var(--gray-900); display: block; margin-bottom: var(--spacing-sm); font-size: 1.1rem; }
.quiz-button {
    background: var(--primary); color: white; border: none;
    padding: var(--spacing-sm) var(--spacing-lg);
    border-radius: var(--radius-md); cursor: pointer;
    font-size: 0.95rem; font-weight: 600; font-family: inherit;
    transition: all var(--transition-base); margin-top: var(--spacing-sm);
}
.quiz-button:hover { background: var(--primary-dark); transform: translateY(-2px); }
.answer { display: none; margin-top: var(--spacing-md); padding: var(--spacing-md); background: var(--gray-50); border-left: 4px solid var(--success); border-radius: var(--radius-md); }
.answer.show { display: block; }

.quiz-question.is-known { border-left-color: var(--success); }
.quiz-question.is-unknown { border-left-color: var(--accent); }
.self-check { display: none; gap: 0.5rem; flex-wrap: wrap; align-items: center; margin-top: var(--spacing-md); font-size: 0.92rem; color: var(--gray-600); }
.self-check.show { display: flex; }
.self-check button {
    border: 2px solid var(--gray-200); background: var(--white); color: var(--gray-700);
    border-radius: var(--radius-full); padding: 0.3rem 0.9rem; font-weight: 600; cursor: pointer; font-family: inherit; font-size: 0.9rem;
}
.self-check button.active.yes { background: var(--success); border-color: var(--success); color: #fff; }
.self-check button.active.no { background: var(--accent-dark); border-color: var(--accent-dark); color: #fff; }

.quiz-score {
    position: sticky; bottom: 12px; z-index: 5;
    display: flex; align-items: center; gap: var(--spacing-md); flex-wrap: wrap;
    background: var(--gray-900); color: #fff;
    border-radius: var(--radius-lg); padding: var(--spacing-sm) var(--spacing-lg);
    margin-top: var(--spacing-lg);
    box-shadow: 0 8px 24px rgba(0,0,0,0.2);
}
.quiz-score .bar { flex: 1; min-width: 120px; height: 8px; background: rgba(255,255,255,0.2); border-radius: 99px; overflow: hidden; }
.quiz-score .bar i { display: block; height: 100%; width: 0; background: var(--success); transition: width 0.3s ease; }
.quiz-score .msg { width: 100%; font-size: 0.92rem; opacity: 0.9; }
.quiz-score .msg:empty { display: none; }

/* ---------- Край на урока: CTA, свързани, навигация ---------- */
.lesson-cta {
    margin-top: var(--spacing-2xl);
    background: linear-gradient(135deg, var(--gray-900) 0%, #1e3a5f 100%);
    color: #fff;
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    display: grid; grid-template-columns: 1fr auto; gap: var(--spacing-lg); align-items: center;
}
.lesson-cta h3 { color: #fff; margin: 0 0 0.4rem; font-size: 1.4rem; }
.lesson-cta p { margin: 0; opacity: 0.9; line-height: 1.6; }
.lesson-cta .cta-actions { display: flex; flex-direction: column; gap: 0.6rem; }
.lesson-cta a {
    display: inline-block; text-align: center; text-decoration: none; font-weight: 700;
    padding: 0.7rem 1.3rem; border-radius: var(--radius-md); white-space: nowrap;
}
.lesson-cta a.primary { background: var(--accent); color: var(--gray-900); }
.lesson-cta a.primary:hover { background: #ffc04d; }
.lesson-cta a.ghost { border: 2px solid rgba(255,255,255,0.5); color: #fff; }
.lesson-cta a.ghost:hover { background: rgba(255,255,255,0.1); }

.related-lessons { margin-top: var(--spacing-2xl); }
.related-lessons h2 { border: none; margin-top: 0; font-size: 1.4rem; color: var(--gray-900); }
.related-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: var(--spacing-md); }
.related-grid a {
    display: flex; gap: 0.75rem; align-items: center;
    background: var(--white); border: 2px solid var(--gray-200); border-radius: var(--radius-lg);
    padding: var(--spacing-md); text-decoration: none; color: var(--gray-900); font-weight: 600;
    transition: all var(--transition-base);
}
.related-grid a:hover { border-color: var(--primary); transform: translateY(-3px); }
.related-grid .ico { font-size: 1.6rem; }
.related-grid small { display: block; color: var(--gray-500); font-weight: 500; font-size: 0.8rem; }

.lesson-pager { display: flex; justify-content: space-between; gap: var(--spacing-md); margin-top: var(--spacing-xl); flex-wrap: wrap; }
.lesson-pager a { color: var(--primary-dark); font-weight: 600; text-decoration: none; max-width: 48%; }
.lesson-pager a:hover { text-decoration: underline; }
.lesson-pager .next { margin-left: auto; text-align: right; }

.source-note { font-size: 0.88rem; color: var(--gray-500); margin-top: var(--spacing-xl); border-top: 1px solid var(--gray-200); padding-top: var(--spacing-md); }

@media (max-width: 768px) {
    .lesson-container { padding: var(--spacing-md); }
    .lesson-header { padding: var(--spacing-xl) var(--spacing-lg); }
    .lesson-card { padding: var(--spacing-lg); }
    .lesson-card h2 { font-size: 1.45rem; }
    .lesson-toc ol { columns: 1; }
    .lesson-cta { grid-template-columns: 1fr; }
    .lesson-pager a { max-width: 100%; }
    .calc-box { padding: var(--spacing-lg); }
}

@media print {
    .navbar, .footer, .reading-progress, .lesson-cta, .related-lessons, .lesson-pager, .quiz-score, .quiz-button, .self-check { display: none !important; }
    .answer { display: block !important; }
}

/* Връзка към учебника */
.book-topics { margin: 2rem 0; padding: 1.25rem 1.4rem; border: 1px solid #cfe3ee; border-radius: 14px; background: #f5fbfe; }
.book-topics h2 { margin: 0 0 .4rem; font-size: 1.15rem; color: #1a365d; }
.book-topics p { margin: 0 0 .8rem; color: #4b5563; font-size: .95rem; }
.book-topics ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 6px; }
.book-topics a { display: block; padding: 9px 12px; border-radius: 10px; background: #fff; border: 1px solid #e3ebf1; text-decoration: none; color: #1a365d; }
.book-topics a:hover { border-color: #3CB4E5; }
.book-topics b { color: #2898c8; margin-right: 6px; font-variant-numeric: tabular-nums; }