:root {
    --primary: #1a4d9c;
    --primary-light: #f0f7ff;
    --accent: #F5A623;
    --danger: #d32f2f;
    --danger-light: #ffebee;
    --success: #388e3c;
    --success-light: #e8f5e9;
    --text-main: #333333;
    --text-secondary: #555555;
    --border: #e2e8f0;
    --bg-color: #f8f9fb;
}

body {
    font-family: 'Open Sans', sans-serif;
    color: var(--text-main);
    background-color: var(--bg-color);
    line-height: 1.6;
    margin: 0;
    padding: 0;
}

.article-container {
    max-width: 900px;
    margin: 40px auto;
    background: #ffffff;
    padding: 40px 60px;
    border-radius: 16px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.05);
}

.article-tag {
    display: inline-block;
    background: rgba(26, 77, 156, 0.1);
    color: var(--primary);
    padding: 6px 14px;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 700;
    margin-bottom: 20px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.article-container h1 { font-size: 2.2rem; font-weight: 800; color: #111; margin-bottom: 24px; line-height: 1.3; }
.article-container h2 { font-size: 1.7rem; font-weight: 700; color: var(--primary); margin-top: 48px; margin-bottom: 20px; border-bottom: 2px solid var(--border); padding-bottom: 8px;}
.article-container h3 { font-size: 1.4rem; font-weight: 700; margin-top: 32px; margin-bottom: 16px; }
.article-container p { font-size: 1.1rem; margin-bottom: 1.2rem; }
.article-container ul, .article-container ol { font-size: 1.1rem; margin-bottom: 1.5rem; padding-left: 1.5rem; }
.article-container li { margin-bottom: 0.8rem; }

.article-hero-img { width: 100%; border-radius: 12px; margin-bottom: 32px; box-shadow: 0 6px 20px rgba(0,0,0,0.08); object-fit: cover; aspect-ratio: 16/9;}

/* Components */
.formula-bubble {
    background: linear-gradient(135deg, #1a4d9c, #2964c2); color: white; padding: 20px 30px;
    border-radius: 12px; font-size: 1.25rem; font-weight: 700; text-align: center;
    margin: 32px 0; box-shadow: 0 8px 24px rgba(26, 77, 156, 0.2);
}

.chem-def {
    background: var(--primary-light); border-left: 5px solid var(--primary);
    padding: 20px; border-radius: 0 12px 12px 0; margin: 24px 0;
}
.chem-def-title { color: var(--primary); font-size: 1.1rem; font-weight: 800; margin: 0 0 8px 0; text-transform: uppercase; letter-spacing: 0.5px; }
.chem-def-text { margin: 0; font-size: 1.05rem; }

.chem-note {
    background: #fff8e1; border-left: 5px solid var(--accent);
    padding: 20px; border-radius: 0 12px 12px 0; margin: 24px 0;
}
.chem-note-title { color: #d88e14; font-size: 1.1rem; font-weight: 800; margin: 0 0 8px 0; text-transform: uppercase; letter-spacing: 0.5px; }
.chem-note-text { margin: 0; font-size: 1.05rem; }

.chem-exception {
    background: var(--danger-light); border-left: 5px solid var(--danger);
    padding: 20px; border-radius: 0 12px 12px 0; margin: 24px 0;
}
.chem-exception-title { color: var(--danger); font-size: 1.1rem; font-weight: 800; margin: 0 0 8px 0; text-transform: uppercase; letter-spacing: 0.5px; }
.chem-exception-text { margin: 0; font-size: 1.05rem; }

.trend-schema { background: white; border: 1px solid var(--border); border-radius: 12px; padding: 24px; margin: 32px 0; text-align: center; box-shadow: 0 4px 12px rgba(0,0,0,0.03); }
.trend-title { font-weight: 800; color: var(--primary); font-size: 1.2rem; margin-bottom: 16px; text-transform: uppercase;}
.trend-arrow-box { display: flex; justify-content: space-around; flex-wrap: wrap; gap: 20px;}
.trend-arrow { padding: 16px 24px; background: #F8FAFC; border: 1px solid var(--border); border-radius: 8px; font-weight: 700; width: 40%; min-width: 200px;}
.trend-arrow span { display: block; font-size: 1.5rem; margin-top: 8px; color: var(--primary);}

/* Task Card */
.task-card {
    background: #fff; border: 1px solid var(--border); border-radius: 12px;
    margin: 40px 0; box-shadow: 0 4px 12px rgba(0,0,0,0.04); transition: box-shadow 0.3s;
    overflow: hidden;
}
.task-card:hover { box-shadow: 0 8px 24px rgba(0,0,0,0.08); }
.task-card-header {
    padding: 20px 24px; display: flex; justify-content: space-between; align-items: center;
    cursor: pointer; background: #fff; transition: background 0.2s;
}
.task-card-header:hover { background: #f8f9fb; }
.task-card-header h4 { margin: 0; font-size: 1.15rem; color: #1a2332; flex: 1; font-weight: 700; }
.task-badge {
    background: linear-gradient(135deg, #F5A623, #e8941a); color: #fff;
    font-size: 0.8rem; font-weight: 700; padding: 0.4rem 0.8rem; border-radius: 6px;
    white-space: nowrap; flex-shrink: 0;
}
.task-card-chevron {
    width: 24px; height: 24px; stroke: #8c9bab; stroke-width: 2.5; fill: none;
    flex-shrink: 0; transition: transform 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}
.task-card.open .task-card-chevron { transform: rotate(180deg); stroke: #F5A623; }
.task-card-condition {
    padding: 0 1.5rem 1rem; font-size: 1.05rem; color: #374151; line-height: 1.6;
    border-bottom: 1px solid #f0f2f5;
}
.task-card-body {
    max-height: 0; opacity: 0; overflow: hidden;
    transition: max-height 0.5s cubic-bezier(0.4, 0, 0.2, 1), opacity 0.35s ease, padding 0.35s ease;
    padding: 0 1.5rem;
}
.task-card.open .task-card-body { max-height: 2000px; opacity: 1; padding: 1.5rem; }

/* Quiz */
.quiz-container { background: #F8FAFC; padding: 32px; border-radius: 12px; margin-top: 48px; border: 1px solid var(--border); }
.quiz-title { font-size: 1.5rem; color: var(--primary); font-weight: 800; margin-bottom: 8px; }
.question-block { display: none; background: white; padding: 24px; border-radius: 8px; margin-top: 24px; box-shadow: 0 2px 4px rgba(0,0,0,0.02); border: 1px solid var(--border); }
.question-block.active { display: block; }
.question-text { font-size: 1.15rem; font-weight: 700; margin-bottom: 20px; }
.option-btn { display: block; width: 100%; text-align: left; background: white; border: 2px solid var(--border); padding: 16px; border-radius: 8px; margin-bottom: 12px; font-size: 1.1rem; cursor: pointer; transition: 0.2s; font-family: 'Open Sans', sans-serif; }
.option-btn:hover:not(:disabled) { border-color: var(--primary); background: #F8FAFC; }
.option-btn.correct { background: #D1FAE5; border-color: #10B981; color: #065F46; }
.option-btn.wrong { background: #FEE2E2; border-color: #EF4444; color: #991B1B; }
.explanation { margin-top: 16px; padding: 16px; background: #F0F9FF; border-radius: 8px; font-size: 1.05rem; display: none; }
.next-btn { margin-top: 24px; background: var(--primary); color: white; border: none; padding: 12px 24px; border-radius: 8px; font-size: 1.1rem; font-weight: 700; cursor: pointer; display: none; font-family: 'Open Sans', sans-serif; }
.result-block { display: none; text-align: center; padding: 40px 0; }
.result-score { font-size: 3rem; font-weight: 900; color: var(--primary); margin-bottom: 16px; }

@media (max-width: 768px) {
    .article-container { padding: 20px; margin: 0; border-radius: 0; }
    .article-container h1 { font-size: 1.8rem; }
    .trend-arrow { width: 100%; }
}