:root{--color-primary: #2563eb;--color-secondary: #10b981;--color-accent: #f59e0b;--color-bg: #f9fafb;--color-surface: #ffffff;--color-text: #1f2937;--color-muted: #6b7280;--shadow-sm: 0 2px 6px rgba(15, 23, 42, .08);--border-radius: 12px;--transition: .15s ease-in-out}*{box-sizing:border-box}html,body{margin:0;padding:0;font-family:Segoe UI,Arial,sans-serif;background-color:var(--color-bg);color:var(--color-text)}body{min-height:100vh;display:flex;flex-direction:column}a{color:inherit}a:focus,button:focus,input:focus,select:focus,textarea:focus{outline:3px solid var(--color-accent);outline-offset:2px}.app-header{background:var(--color-primary);color:#fff;padding:1rem 1.5rem;display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:1rem;box-shadow:var(--shadow-sm)}.app-header .brand{display:flex;align-items:center;gap:.75rem}.app-header .brand-icon{font-size:1.8rem}.app-header h1{margin:0;font-size:1.5rem}nav{display:flex;gap:.5rem;flex-wrap:wrap}.nav-btn{border:none;border-radius:999px;padding:.6rem 1.1rem;background:rgba(255,255,255,.15);color:#fff;font-weight:600;cursor:pointer;transition:background var(--transition),transform var(--transition)}.nav-btn:hover,.nav-btn:focus-visible{background:rgba(255,255,255,.3)}.nav-btn[disabled]{opacity:.4;cursor:not-allowed}main{flex:1;padding:1.5rem}.view{display:none;gap:1.5rem}.view.active{display:block}.card-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:1.2rem;margin-top:1.5rem}.card{background:var(--color-surface);border-radius:var(--border-radius);padding:1.5rem;box-shadow:var(--shadow-sm);transition:transform var(--transition),box-shadow var(--transition);cursor:pointer}.card:hover,.card:focus-visible{transform:translateY(-4px);box-shadow:0 12px 30px rgba(37,99,235,.18)}.section-header{display:flex;flex-direction:column;gap:1rem;margin-bottom:1rem}.section-header h2{margin:0}.section-header p{margin:0;color:var(--color-muted)}.view-controls{display:flex;flex-wrap:wrap;gap:.5rem}.view-controls .sim-btn{background:#dbeafe;color:var(--color-primary);border:1px solid rgba(37,99,235,.2)}.view-controls .sim-btn.active{background:var(--color-primary);color:#fff}.view-controls .sim-btn:focus-visible{background:var(--color-primary);color:#fff}.button-row{display:flex;flex-wrap:wrap;gap:.75rem}.button-row button{border:none;border-radius:8px;padding:.55rem 1.2rem;margin-bottom:10px;background:var(--color-secondary);color:#fff;font-weight:600;cursor:pointer;transition:background var(--transition),opacity var(--transition)}.button-row button:hover,.button-row button:focus-visible{background:#0f9c7a}.button-row button:disabled{background:#d1d5db;color:#6b7280;cursor:not-allowed}label{display:flex;flex-direction:column;gap:.4rem;font-weight:600;margin-bottom:1rem}input[type=range]{width:100%}output{font-weight:700;color:var(--color-primary)}textarea{width:100%;border-radius:8px;border:1px solid #e5e7eb;padding:.75rem;font-family:inherit;resize:vertical}select{border-radius:8px;border:1px solid #e5e7eb;padding:.5rem;font-size:1rem}.app-footer{background:#111827;color:#d1d5db;padding:.9rem 1.5rem;text-align:center}.glossary{background:var(--color-surface);border-radius:var(--border-radius);padding:1rem 1.5rem;box-shadow:var(--shadow-sm);max-width:600px}details{background:var(--color-surface);border-radius:var(--border-radius);padding:1rem 1.2rem;box-shadow:var(--shadow-sm);margin-bottom:1rem}details[open] summary{color:var(--color-primary)}summary{cursor:pointer;font-weight:700}.intro{max-width:600px;color:var(--color-muted)}.simulation-panels{display:grid;gap:1.5rem}.sim-panel{display:none;gap:1.5rem}.sim-panel.active{display:block}.simulation-layout{display:grid;grid-template-columns:minmax(260px,2fr) minmax(240px,1fr);gap:1.5rem;margin-bottom:1.5rem}.canvas-panel,.control-panel{background:var(--color-surface);border-radius:var(--border-radius);padding:1rem 1.5rem;box-shadow:var(--shadow-sm)}.canvas-panel{display:flex;align-items:center;justify-content:center;min-height:360px}#simulation-canvas,#forces-canvas,#projectile-canvas,#charge-canvas{width:100%;max-width:600px;height:auto;border:2px solid #e5e7eb;border-radius:12px;background:linear-gradient(180deg,#f9fafb 0%,#e5e7eb 100%)}.results-panel{display:grid;grid-template-columns:repeat(auto-fit,minmax(260px,1fr));gap:1.5rem;margin-bottom:1.5rem}.results-values{display:grid;gap:1rem}.results-values ul{list-style:none;padding:0;margin:0}.results-values li{background:var(--color-surface);border-radius:10px;padding:.8rem 1rem;box-shadow:var(--shadow-sm);display:flex;justify-content:space-between;align-items:center}.chart-container{background:var(--color-surface);border-radius:var(--border-radius);padding:1rem 1.5rem;box-shadow:var(--shadow-sm)}.learning-support{display:grid;gap:1rem}@media (max-width: 1024px){.simulation-layout{grid-template-columns:1fr}.canvas-panel{order:-1}}@media (max-width: 768px){nav{width:100%;justify-content:center}.app-header{text-align:center}main{padding:1rem}.card{padding:1.2rem}.canvas-panel,.control-panel,.chart-container{padding:1rem}}@media (max-width: 480px){.app-header h1{font-size:1.2rem}.nav-btn{flex:1 1 100%;justify-content:center}#simulation-canvas{max-width:100%}}