.app{display:flex;min-height:100vh}.sidebar{width:260px;min-width:260px;background:var(--s1);border-right:1px solid var(--border);position:sticky;top:0;height:100vh;overflow-y:auto;display:flex;flex-direction:column}.sidebar-header{padding:1.2rem 1rem;border-bottom:1px solid var(--border)}.sidebar-logo{font-family:var(--mono);font-weight:700;font-size:.75rem;color:var(--cyan);letter-spacing:2px;text-transform:uppercase}.sidebar-title{font-family:var(--sans);font-weight:900;font-size:1.05rem;color:var(--text);line-height:1.3;margin-top:.3rem}.sidebar nav{flex:1;overflow-y:auto;min-height:0}.nav-section{padding:.5rem 0}.nav-label{padding:.4rem 1rem;font-size:.65rem;font-family:var(--mono);color:var(--muted);text-transform:uppercase;letter-spacing:1.5px}.nav-item{display:flex;align-items:center;gap:.6rem;padding:.55rem 1rem;cursor:pointer;font-size:.83rem;color:var(--muted);transition:all .15s;border-left:2px solid transparent;text-decoration:none}.nav-item:hover{color:var(--text);background:var(--s2)}.nav-item.active{color:var(--cyan);border-left-color:var(--cyan);background:#22d3ee0d}.nav-item .num{font-family:var(--mono);font-size:.65rem;background:var(--s3);padding:.1rem .4rem;border-radius:4px;min-width:22px;text-align:center;flex-shrink:0}.sidebar-lecture-nav{margin-top:auto;padding:1rem;border-top:1px solid var(--border);display:flex;gap:.5rem;flex-shrink:0}.sidebar-lecture-nav a,.sidebar-lecture-nav span{flex:1;display:flex;align-items:center;justify-content:center;gap:.4rem;padding:.6rem .8rem;font-size:.8rem;font-weight:500;border-radius:6px;text-decoration:none;transition:all .2s}.sidebar-lecture-nav a{color:var(--text);background:var(--s2);border:1px solid var(--border)}.sidebar-lecture-nav a:hover{color:var(--cyan);border-color:var(--cyan);background:#22d3ee14}.sidebar-lecture-nav span.sidebar-nav-disabled{color:var(--muted);opacity:.5;cursor:not-allowed}.main{flex:1;overflow-x:hidden}.hero{background:linear-gradient(160deg,#07090f,#0a0f1e 40%,#0d0a1a);border-bottom:1px solid var(--border);padding:3.5rem 3rem 2.5rem;position:relative;overflow:hidden}.hero:after{content:"";position:absolute;top:0;left:0;right:0;bottom:0;background:radial-gradient(ellipse 60% 40% at 20% 50%,rgba(34,211,238,.06) 0%,transparent 70%),radial-gradient(ellipse 40% 60% at 80% 30%,rgba(167,139,250,.05) 0%,transparent 70%);pointer-events:none}.hero-tag{font-family:var(--mono);font-size:.7rem;color:var(--cyan);letter-spacing:3px;text-transform:uppercase;margin-bottom:.8rem}.hero h1{font-weight:900;font-size:clamp(1.8rem,4vw,2.8rem);line-height:1.1;margin-bottom:.8rem}.hero h1 span{color:var(--cyan)}.hero p,.hero-desc{color:var(--muted);font-size:.95rem;max-width:540px;line-height:1.6}.hero-chips{display:flex;flex-wrap:wrap;gap:.4rem;margin-top:1.2rem}.chip{font-family:var(--mono);font-size:.7rem;padding:.25rem .7rem;border-radius:99px;border:1px solid}.chip-c{color:var(--cyan);border-color:#22d3ee4d;background:#22d3ee0f}.chip-o{color:var(--orange);border-color:#fb923c4d;background:#fb923c0f}.chip-g{color:var(--green);border-color:#4ade804d;background:#4ade800f}.section,section[id]{padding:2.5rem 3rem;border-bottom:1px solid var(--border);max-width:100%;overflow-x:hidden}section[id]{scroll-margin-top:2rem}.section:last-child,section[id]:last-child{border-bottom:none}section[id] h2{font-weight:900;font-size:1.8rem;line-height:1.2;margin-bottom:.8rem;color:var(--text);margin-top:0}section[id] h3{font-weight:700;font-size:1.3rem;line-height:1.3;margin:2rem 0 1rem;color:var(--text)}section[id] h4{font-weight:600;font-size:1.05rem;line-height:1.4;margin:1.5rem 0 .8rem;color:var(--cyan)}.section-lead{font-size:1.05rem;line-height:1.7;color:var(--muted);margin-bottom:2rem;max-width:800px}.section-lead .bangla{display:block;margin-top:.5rem;font-family:Hind Siliguri,sans-serif;color:var(--muted);font-size:.95rem}.slide-badge{display:inline-flex;align-items:center;gap:.5rem;font-family:var(--mono);font-size:.68rem;color:var(--muted);background:var(--s2);border:1px solid var(--border);padding:.3rem .8rem;border-radius:6px;margin-bottom:1rem}.slide-badge span{color:var(--cyan);font-weight:600}.section-h{font-weight:900;font-size:1.5rem;line-height:1.2;margin-bottom:.5rem;color:var(--text)}.section-h em{font-style:normal;color:var(--cyan)}.section-sub{color:var(--muted);font-size:.9rem;margin-bottom:1.5rem;max-width:680px}@media (max-width: 800px){.sidebar{position:fixed;left:-280px;top:0;z-index:1000;transition:left .3s cubic-bezier(.4,0,.2,1);box-shadow:none}body.mobile-nav-open .sidebar{left:0;box-shadow:8px 0 30px #02061780}.section{padding:2rem 1.2rem}section[id]{padding:2rem 1.2rem}.hero{padding:2rem 1.2rem}}