/* FreeStudyAdda Physics Lab — light, viewport-aware, browser-only */
:root{color-scheme:light;--ink:#16243d;--muted:#68778e;--line:#e6ebf4;--blue:#4162e8;--indigo:#6255ea;--sky:#06a5c8;--bg:#f6f8ff;--card:#fff;--good:#139b83;--red:#e46a70;--shadow:0 8px 28px rgba(35,51,91,.055);font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif}
*,*::before,*::after{box-sizing:border-box}html,body{margin:0;min-height:100%;background:var(--bg);color:var(--ink)}body{overflow:hidden}button,input,select{font:inherit}button{cursor:pointer}button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible{outline:3px solid #a5c5ff;outline-offset:3px}a{text-decoration:none;color:inherit}button[disabled]{cursor:not-allowed;opacity:.55}
.header{height:73px;display:flex;align-items:center;gap:18px;justify-content:space-between;padding:12px clamp(14px,2.1vw,34px);background:#fff;border-bottom:1px solid var(--line);position:relative;z-index:2}
.brand{display:flex;align-items:center;gap:12px;min-width:0}.brand-mark{width:43px;height:43px;display:grid;place-items:center;background:linear-gradient(140deg,#4162e8,#34b7d5);color:#fff;border-radius:15px;font-size:24px;box-shadow:0 5px 14px #4162e833}.brand strong{font-size:18px;letter-spacing:-.5px;display:block}.brand small{display:block;color:var(--muted);font-size:11px}.header-middle{display:flex;align-items:center;gap:7px;color:#7a86a3;font-size:12px;font-weight:650}.header-middle b{color:var(--blue)}.header-tools{display:flex;align-items:center;gap:8px;flex-wrap:wrap}.locale{background:#f3f5fd;border:1px solid var(--line);padding:7px 9px;border-radius:12px;color:#66728e;font-size:12px;font-weight:800}.locale.active{color:#fff;background:var(--blue);border-color:var(--blue)}.header-link{border:1px solid var(--line);border-radius:12px;background:white;padding:8px 12px;font-weight:750;font-size:12px}
.shell{height:calc(100dvh - 73px);min-height:0;display:grid;grid-template-columns:253px minmax(0,1fr)}
.sidebar{background:#fff;border-right:1px solid var(--line);padding:23px 15px;display:flex;flex-direction:column;min-height:0;overflow:auto}.nav-kicker{font-size:10px;letter-spacing:1.2px;text-transform:uppercase;color:#98a2b7;font-weight:850;padding:4px 12px 11px}.nav-list{display:flex;flex-direction:column;gap:3px}.nav-item{display:flex;align-items:center;gap:13px;padding:12px 13px;border-radius:12px;font-weight:720;color:#627087;font-size:13px;transition:.18s}.nav-item:hover{background:#f4f6ff;color:var(--blue)}.nav-item.active{background:#eaf0ff;color:#3357dc}.nav-icon{width:24px;text-align:center;font-size:19px}.sidebar-bottom{margin-top:auto;display:grid;gap:12px;padding-top:20px}.info-card{background:linear-gradient(148deg,#eaf1ff,#f1f6ff);border:1px solid #dce7fc;padding:16px;border-radius:16px}.info-card b{font-size:13px;color:#3357dc}.info-card p{font-size:12px;color:#697893;line-height:1.6;margin:8px 0 0}.micro{font-size:11px;color:#8d99ad;text-align:center}
.main{overflow:auto;padding:clamp(16px,2vw,29px);min-width:0;min-height:0}.page-width{max-width:1440px;margin:auto}.page-head{display:flex;justify-content:space-between;align-items:center;gap:15px;margin-bottom:18px}.kicker{display:flex;gap:8px;align-items:center;color:var(--blue);font-size:11px;font-weight:850;letter-spacing:1.1px;text-transform:uppercase;margin:0 0 8px}.page-head h1{font-size:clamp(24px,2.3vw,35px);letter-spacing:-1.5px;line-height:1.2;margin:0}.sub{font-size:13px;color:var(--muted);line-height:1.65;margin:8px 0 0;max-width:790px}.level-control{display:flex;gap:4px;background:#fff;border:1px solid var(--line);padding:5px;border-radius:14px;flex-shrink:0}.level-control button{border:0;border-radius:10px;background:transparent;color:#7b8699;font-size:11px;font-weight:780;padding:9px 10px}.level-control button.active{background:#eaf0ff;color:#3659de}
.card{background:var(--card);border:1px solid var(--line);border-radius:19px;box-shadow:var(--shadow)}.lab-layout{display:grid;grid-template-columns:minmax(0,1.65fr) minmax(290px,.9fr);gap:17px;align-items:start}.lab-left,.lab-right{display:grid;gap:16px;min-width:0}.card-head{padding:17px 18px 13px;display:flex;justify-content:space-between;gap:10px;align-items:center}.card-title{font-size:15px;font-weight:850;letter-spacing:-.2px}.card-sub{color:var(--muted);font-size:11px;margin-top:4px}.chip{padding:5px 9px;background:#e9f7f5;color:#148a77;border-radius:999px;font-size:10px;font-weight:850;white-space:nowrap}.canvas-box{position:relative;margin:0 16px 16px;border-radius:15px;overflow:hidden;background:radial-gradient(ellipse at 28% 15%,#f3faff,#e8efff 68%,#eaf3ff);border:1px solid #dde7f9}.canvas-box canvas{display:block;width:100%;height:clamp(235px,38vh,420px);touch-action:pan-y}.canvas-overlay{position:absolute;top:13px;left:13px;display:flex;gap:7px;flex-wrap:wrap;pointer-events:none}.canvas-badge{background:#ffffffd9;border:1px solid #dce7fb;border-radius:9px;color:#43598a;box-shadow:0 3px 9px #30426f0d;padding:7px 10px;font-weight:800;font-size:11px;backdrop-filter:blur(6px)}.sim-actions{display:flex;gap:8px;padding:0 16px 17px;flex-wrap:wrap}.btn{padding:11px 15px;border:1px solid var(--line);border-radius:12px;font-size:12px;font-weight:800;background:#fff;color:#435374}.btn:hover{background:#f4f6fe}.btn.primary{background:var(--blue);color:#fff;border-color:var(--blue)}.btn.primary:hover{background:#334fd0}.btn.ghost{background:#eef2ff;border-color:#eef2ff;color:#3559d6}.btn:disabled{opacity:.5}
.controls{padding:12px 18px 19px}.slider-wrap{display:grid;gap:9px;margin:0 0 19px}.slider-top{display:flex;justify-content:space-between;gap:8px;font-size:12px;color:#6e7b93;font-weight:730}.slider-top output{font-variant-numeric:tabular-nums;color:#2849cf;font-weight:850}.slider-wrap input{width:100%;accent-color:var(--blue);cursor:pointer}.slider-wrap select{padding:9px;background:#f9faff;border:1px solid var(--line);border-radius:10px;color:var(--ink);font-weight:750}.stats{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:9px;padding:0 17px 17px}.stat{background:#f7f9ff;border:1px solid #ebeffc;border-radius:13px;padding:12px}.stat-label{font-size:10px;text-transform:uppercase;letter-spacing:.65px;font-weight:850;color:#8590a7}.stat-value{margin-top:8px;font-size:clamp(17px,1.7vw,23px);font-weight:850;letter-spacing:-.6px;font-variant-numeric:tabular-nums;color:#223c8e}.stat-unit{font-size:10px;font-weight:750;margin-left:4px;color:#7684a0}
.teach-panel{padding:19px}.teach-panel h3{margin:0 0 10px;font-size:14px}.teach-panel p{font-size:12px;color:#65738a;line-height:1.75;margin:8px 0}.formula-bubble{display:inline-flex;flex-wrap:wrap;gap:6px;align-items:center;margin:6px 0 10px;padding:10px 13px;border-radius:11px;background:#eef2ff;color:#304cc6;font-size:17px;font-weight:850;letter-spacing:.2px}.tip{border-left:3px solid #36a5c5;padding:10px 12px;background:#f1fbff;color:#536a84;border-radius:0 10px 10px 0;font-size:12px;line-height:1.65}.two-actions{display:flex;gap:8px;flex-wrap:wrap;margin-top:14px}
.dashboard-banner{background:linear-gradient(110deg,#334cbd 0%,#506be8 54%,#27b1ce 110%);border-radius:21px;color:#fff;padding:27px;position:relative;overflow:hidden;margin-bottom:20px}.dashboard-banner:after{content:"⚛";position:absolute;right:40px;top:-35px;font-size:170px;opacity:.12;pointer-events:none}.banner-pill{font-size:11px;font-weight:750;color:#d9e6ff;background:#ffffff24;border:1px solid #ffffff2e;border-radius:999px;padding:7px 11px;display:inline-block}.dashboard-banner h2{font-size:clamp(25px,3vw,42px);letter-spacing:-1.6px;max-width:690px;margin:16px 0 8px}.dashboard-banner p{line-height:1.7;font-size:13px;max-width:580px;color:#e7edff}.dashboard-banner .btn{margin-top:10px;background:#fff;border:0;color:#3658d0}.modules{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:14px}.module{padding:19px;position:relative;overflow:hidden;transition:transform .15s,border-color .15s;min-height:174px}.module:hover{transform:translateY(-3px);border-color:#b9c9fa}.module-ico{width:46px;height:46px;border-radius:14px;display:grid;place-items:center;font-size:24px;background:#eff3ff;margin-bottom:18px}.module h3{font-size:15px;letter-spacing:-.25px;margin:0 0 7px}.module p{margin:0;color:#7c899c;font-size:12px;line-height:1.55}.module .arrow{position:absolute;right:16px;top:21px;color:#a0abc1;font-size:19px}
.section-line{display:flex;justify-content:space-between;align-items:center;margin:19px 0 13px;gap:10px}.section-line h2{margin:0;font-size:17px}.small-muted{font-size:12px;color:var(--muted)}.quick-row{display:flex;gap:10px;flex-wrap:wrap}.quick-row a{padding:10px 14px;border:1px solid var(--line);background:#fff;border-radius:12px;color:#526686;font-size:12px;font-weight:750}
.search-input{padding:12px 14px;width:100%;max-width:350px;border-radius:12px;border:1px solid var(--line);background:white;outline-color:var(--blue)}.formulas{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:13px}.formula-card{padding:19px}.formula-card .topic{font-size:11px;font-weight:850;color:#4564d9;text-transform:uppercase;letter-spacing:.7px}.formula-card h3{margin:7px 0 12px;font-size:14px}.formula-display{font-size:21px;font-weight:850;color:#2646c5;margin:0 0 10px}.formula-card p{font-size:12px;color:var(--muted);margin:0;line-height:1.6}
.quiz-intro{padding:23px;margin-bottom:15px}.quiz-progress{background:#e8edfb;border-radius:20px;height:8px;margin-top:15px;overflow:hidden}.quiz-progress div{height:100%;background:linear-gradient(90deg,#4263eb,#19b5c5);transition:width .2s}.question-card{padding:25px}.question-count{font-size:11px;font-weight:850;color:var(--blue)}.question-card h2{font-size:clamp(19px,2.2vw,25px);margin:13px 0 20px;max-width:700px}.choices{display:grid;gap:11px}.choice{width:100%;background:#f9faff;text-align:left;border:1px solid var(--line);padding:15px 16px;border-radius:12px;font-weight:650;color:#3b4b65;display:flex;gap:13px;align-items:center}.choice .letter{width:29px;height:29px;border:1px solid #d9e2fa;border-radius:9px;display:grid;place-items:center;font-size:11px;font-weight:900;color:#5670d9;background:#fff;flex-shrink:0}.choice.selected{border-color:#4162e8;background:#eef2ff}.choice.correct{border-color:#26a68b;background:#ecfaf6}.choice.wrong{border-color:#ed8392;background:#fff0f3}.quiz-foot{display:flex;justify-content:space-between;align-items:center;gap:14px;margin-top:20px}.score{font-size:38px;color:#3656d0;font-weight:900}.explain{padding:13px;background:#effaf7;border-radius:12px;border:1px solid #d4efe6;font-size:12px;line-height:1.7;color:#276957;margin-top:17px}
@media(max-width:1180px){.modules{grid-template-columns:repeat(3,minmax(0,1fr))}.lab-layout{grid-template-columns:minmax(0,1.3fr) minmax(270px,1fr)}.header-middle{display:none}}
@media(max-width:950px){body{overflow:auto}.header{height:auto;min-height:70px}.shell{height:auto;display:block}.sidebar{padding:10px 13px;border-right:0;border-bottom:1px solid var(--line);overflow:visible}.nav-kicker,.sidebar-bottom{display:none}.nav-list{display:flex;flex-direction:row;overflow-x:auto;scrollbar-width:thin;gap:7px}.nav-item{flex:0 0 auto;white-space:nowrap;padding:10px 13px}.main{overflow:visible}.lab-layout{grid-template-columns:1fr}.lab-right{grid-template-columns:repeat(2,minmax(0,1fr));align-items:start}.lab-right>.card:last-child{grid-column:1/-1}.canvas-box canvas{height:clamp(280px,42vh,430px)}}
@media(max-width:680px){.header{gap:9px;padding:10px 13px;flex-wrap:wrap}.brand strong{font-size:15px}.brand small{font-size:10px}.brand-mark{width:37px;height:37px;font-size:19px}.header-tools{margin-left:auto}.header-link{display:none}.main{padding:14px}.page-head{display:block}.level-control{width:100%;overflow-x:auto;margin-top:13px}.level-control button{flex:1;white-space:nowrap}.modules{grid-template-columns:repeat(2,minmax(0,1fr));gap:10px}.module{min-height:165px;padding:15px}.module-ico{width:40px;height:40px;font-size:21px;margin-bottom:13px}.module h3{font-size:13px}.module p{font-size:11px}.dashboard-banner{padding:23px 20px}.dashboard-banner:after{right:-5px;font-size:125px}.lab-right{grid-template-columns:1fr}.lab-right>.card:last-child{grid-column:auto}.canvas-box{margin:0 10px 12px}.canvas-box canvas{height:clamp(260px,40vh,340px)}.sim-actions{padding:0 10px 13px}.formulas{grid-template-columns:1fr}.stats{grid-template-columns:repeat(2,minmax(0,1fr))}.stat{padding:11px}.question-card{padding:16px}}
@media(max-width:365px){.modules{grid-template-columns:1fr}.header-tools{width:100%;justify-content:flex-end}.page-head h1{font-size:23px}}
@media(prefers-reduced-motion:reduce){*,*::before,*::after{animation:none!important;transition:none!important}}
@media print{body{overflow:visible;background:#fff}.header,.sidebar,.level-control,.sim-actions{display:none!important}.shell{display:block;height:auto}.main{overflow:visible}.page-width{max-width:none}.card{break-inside:avoid;box-shadow:none}.canvas-box canvas{height:250px}}