/* Forces and friction lab (Zaid Berjis). Every rule is scoped to .labapp. */
.labapp {
  --bg: #ffffff; --fg: #14171c; --muted: #56606c; --line: #dde1e6; --panel: #f5f7fa; --panel2: #eaeef3;
  --weight: #c62828; --normal: #1f5fbf; --friction: #d46a00; --applied: #1b8a3c; --net: #7b3fa6; --vel: #56606c;
  --ramp: #e6ebf1; --rampedge: #4d5763; --block: #f1dcb8; --blockedge: #8a6a3c;
  --accent: #1f5fbf; --ok: #1b8a3c; --bad: #c62828;
  --display: var(--font-head);
  --body: var(--font-body);
  --mono: ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
  --math: "KaTeX_Main", "Times New Roman", Times, serif;
  font-size: 17px; line-height: 1.55; color: var(--fg); font-family: var(--body); margin: 24px 0 8px;
}
html.big .labapp { font-size: 21px; }
/* Layout: masthead, sticky tab rail, then one lab per tab — figure column left, controls and worked math right. */
.labapp .dragzone { touch-action: none; -webkit-user-select: none; user-select: none; }
.labapp .grip { fill: var(--c); fill-opacity: 0.16; stroke: var(--c); stroke-width: 2; stroke-dasharray: 4 3; }
.labapp .hint { font-size: 0.9em; color: var(--muted); }
.labapp .forcekey { display: flex; flex-wrap: wrap; gap: 8px 18px; margin-top: 14px; font-size: 0.9em; }
.labapp .forcekey span { display: inline-flex; align-items: center; gap: 7px; }
.labapp .forcekey i.sw { display: inline-block; width: 22px; height: 4px; border-radius: 2px; background: var(--c); }
.labapp .tabbar { position: sticky; top: env(safe-area-inset-top, 0px); z-index: 10; background: var(--bg); border-bottom: 1px solid var(--line); }
.labapp .tabs { display: flex; gap: 4px; overflow-x: auto; align-items: stretch; scrollbar-width: thin; }
.labapp .tabs button[role="tab"] { font: 500 0.98em var(--body); color: var(--muted); background: none; border: 0; border-bottom: 3px solid transparent; padding: 14px 14px 11px; cursor: pointer; white-space: nowrap; }
.labapp .tabs button[role="tab"][aria-selected="true"] { color: var(--fg); border-bottom-color: var(--accent); }
.labapp .tabs button[role="tab"]:hover { color: var(--fg); }
.labapp .sizebtn { margin-left: auto; align-self: center; white-space: nowrap; }
.labapp .tab { display: grid; gap: 20px; }
.labapp .sechead { display: flex; flex-wrap: wrap; align-items: baseline; gap: 8px 16px; }
.labapp .ref { font: 500 0.8em var(--mono); color: var(--muted); border: 1px solid var(--line); border-radius: 999px; padding: 3px 10px; letter-spacing: 0.02em; }
.labapp .intro { max-width: 78ch; color: var(--fg); }
.labapp .lab { display: grid; grid-template-columns: minmax(0, 1.6fr) minmax(0, 1fr); gap: 24px; align-items: start; }
.labapp .figs { display: grid; gap: 16px; min-width: 0; }
.labapp .figrow { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 16px; }
.labapp .side { display: grid; gap: 16px; min-width: 0; align-content: start; }
@media (max-width: 1020px) { .labapp .lab { grid-template-columns: minmax(0, 1fr); } }
@media (max-width: 680px) { .labapp .figrow { grid-template-columns: minmax(0, 1fr); } }
.labapp .card { background: var(--panel); border: 1px solid var(--line); border-radius: 10px; padding: 14px 16px; margin: 0; min-width: 0; }
.labapp figure.card { display: grid; gap: 6px; }
.labapp figcaption, .labapp .cardtitle { font: 500 0.76em var(--mono); text-transform: uppercase; letter-spacing: 0.1em; color: var(--muted); }
.labapp svg.fig { width: 100%; height: auto; display: block; overflow: visible; }
.labapp .chips { display: flex; flex-wrap: wrap; gap: 8px; }
.labapp .chip { font: 500 0.92em var(--body); padding: 8px 14px; border-radius: 999px; border: 1px solid var(--line); background: var(--bg); color: var(--fg); cursor: pointer; }
.labapp .chip[aria-pressed="true"] { background: var(--fg); color: var(--bg); border-color: var(--fg); }
.labapp .seg { display: inline-flex; border: 1px solid var(--line); border-radius: 8px; overflow: hidden; width: fit-content; max-width: 100%; flex-wrap: wrap; }
.labapp .seg button { font: 500 0.92em var(--body); padding: 8px 14px; border: 0; background: var(--bg); color: var(--muted); cursor: pointer; }
.labapp .seg button + button { border-left: 1px solid var(--line); }
.labapp .seg button[aria-pressed="true"] { background: var(--panel2); color: var(--fg); }
.labapp .btn { font: 500 0.92em var(--body); padding: 9px 16px; border-radius: 8px; border: 1px solid var(--line); background: var(--bg); color: var(--fg); cursor: pointer; }
.labapp .btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.labapp .btn:disabled { opacity: 0.5; cursor: default; }
.labapp .btns { display: flex; flex-wrap: wrap; gap: 8px; }
.labapp button:focus-visible, .labapp input:focus-visible, .labapp select:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
.labapp .ctls { display: grid; gap: 12px; }
.labapp .ctl label { display: flex; justify-content: space-between; align-items: baseline; gap: 12px; font-size: 0.95em; }
.labapp .ctl output { font: 500 0.95em var(--mono); font-variant-numeric: tabular-nums; color: var(--fg); white-space: nowrap; }
.labapp .ctl input[type="range"] { width: 100%; accent-color: var(--accent); height: 28px; margin: 2px 0 0; }
.labapp .ctl.disabled { opacity: 0.45; }
.labapp .sel { display: grid; gap: 4px; font-size: 0.95em; }
.labapp select { font: 0.95em var(--body); padding: 8px 10px; border-radius: 8px; border: 1px solid var(--line); background: var(--bg); color: var(--fg); max-width: 100%; }
.labapp .chk { display: flex; align-items: center; gap: 8px; font-size: 0.95em; cursor: pointer; }
.labapp .chk input { width: 18px; height: 18px; accent-color: var(--accent); }
.labapp i.m, .labapp .sym { font-family: var(--math); font-style: italic; font-size: 1.08em; }
.labapp .sym sub { font-style: normal; font-size: 0.72em; }
.labapp .legend { width: 100%; border-collapse: collapse; font-size: 0.93em; }
.labapp .legend td { padding: 6px 4px; border-bottom: 1px solid var(--line); vertical-align: middle; }
.labapp .legend td.v { text-align: right; font-family: var(--mono); font-variant-numeric: tabular-nums; white-space: nowrap; }
.labapp .legend .sw { display: inline-block; width: 22px; height: 4px; border-radius: 2px; background: var(--c); vertical-align: middle; }
.labapp .legend .dash { background: repeating-linear-gradient(90deg, var(--c) 0 6px, transparent 6px 10px); }
.labapp .eqs { display: grid; gap: 10px; font-size: 1.05em; overflow-x: auto; }
.labapp .eqs .row { overflow-x: auto; overflow-y: hidden; }
.labapp .eqs .note { font-size: 0.93em; color: var(--muted); }
.labapp .eqs .step { font: 500 0.75em var(--mono); text-transform: uppercase; letter-spacing: 0.1em; color: var(--muted); margin-top: 4px; }
.labapp mjx-container { max-width: 100%; }
.labapp mjx-container[display="true"] { margin: 0.35em 0 !important; }
.labapp .cw { fill: var(--weight); stroke: var(--weight); }
.labapp .cn { fill: var(--normal); stroke: var(--normal); }
.labapp .cf { fill: var(--friction); stroke: var(--friction); }
.labapp .ca { fill: var(--applied); stroke: var(--applied); }
.labapp .cnet { fill: var(--net); stroke: var(--net); }
.labapp .status { display: inline-flex; align-items: center; gap: 8px; font: 600 0.92em var(--body); padding: 6px 12px; border-radius: 999px; border: 1.5px solid var(--c); color: var(--c); width: fit-content; }
.labapp .status::before { content: ""; width: 9px; height: 9px; border-radius: 50%; background: var(--c); }
.labapp .readouts { display: grid; grid-template-columns: repeat(auto-fit, minmax(128px, 1fr)); gap: 10px; }
.labapp .ro { background: var(--bg); border: 1px solid var(--line); border-radius: 8px; padding: 8px 10px; min-width: 0; }
.labapp .ro .k { font-size: 0.82em; color: var(--muted); }
.labapp .ro .v { font: 500 1.12em var(--mono); font-variant-numeric: tabular-nums; white-space: nowrap; }
.labapp .cands { display: grid; gap: 8px; }
.labapp .cands label { display: flex; gap: 10px; align-items: flex-start; font-size: 0.95em; cursor: pointer; }
.labapp .cands input { width: 18px; height: 18px; margin-top: 3px; accent-color: var(--accent); flex: none; }
.labapp .fb { display: grid; gap: 8px; font-size: 0.93em; }
.labapp .fb div { padding: 8px 10px; border-radius: 8px; border-left: 4px solid var(--c); background: var(--bg); }
.labapp .fb b { color: var(--c); }
.labapp .bars { display: grid; gap: 10px; }
.labapp .bar { display: grid; grid-template-columns: 4.2em minmax(0, 1fr) 6.5em; gap: 10px; align-items: center; }
.labapp .bar .track { height: 16px; background: var(--panel2); border-radius: 4px; overflow: hidden; }
.labapp .bar .fill { height: 100%; background: var(--c); border-radius: 4px; transition: width 0.15s; }
.labapp .bar .val { font: 500 0.95em var(--mono); text-align: right; font-variant-numeric: tabular-nums; }
.labapp .steps { margin: 0; padding-left: 1.3em; display: grid; gap: 6px; max-width: 80ch; }
.labapp .concepts { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 16px; }
.labapp .concepts .card p + p { margin-top: 8px; }
.labapp .quote { font-family: var(--display); font-size: 1.02em; font-weight: 500; }
.labapp details { background: var(--bg); border: 1px solid var(--line); border-radius: 8px; padding: 10px 12px; }
.labapp details summary { cursor: pointer; font-weight: 600; }
.labapp details[open] summary { margin-bottom: 8px; }
.labapp table.mu { width: 100%; border-collapse: collapse; font-size: 0.93em; }
.labapp table.mu th, .labapp table.mu td { padding: 7px 8px; border-bottom: 1px solid var(--line); text-align: left; }
.labapp table.mu td.n, .labapp table.mu th.n { text-align: right; font-family: var(--mono); font-variant-numeric: tabular-nums; }
.labapp table.mu tbody tr { cursor: pointer; }
.labapp table.mu tbody tr:hover { background: var(--panel2); }
.labapp table.mu tbody tr.on { background: var(--panel2); box-shadow: inset 4px 0 0 var(--accent); }
.labapp table.mu tbody tr.na { cursor: default; color: var(--muted); }
.labapp .tablewrap { overflow-x: auto; }
.labapp .presets { display: grid; gap: 8px; }
.labapp .preset { text-align: left; font: 0.93em var(--body); padding: 10px 12px; border-radius: 8px; border: 1px solid var(--line); background: var(--bg); color: var(--fg); cursor: pointer; display: grid; gap: 2px; }
.labapp .preset small { color: var(--muted); font: 0.76em var(--mono); letter-spacing: 0.03em; }
.labapp .preset[aria-pressed="true"] { border-color: var(--accent); box-shadow: inset 4px 0 0 var(--accent); }
.labapp .problem { font-size: 1em; }
.labapp .problem .q { margin-top: 6px; font-weight: 600; }
.labapp .hide-ans .ans { filter: blur(10px); pointer-events: none; user-select: none; }
.labapp .hide-ans .ans-wrap { position: relative; }
/* SVG styling */
.labapp .fig text { font-family: var(--body); }
.labapp .ground { stroke: var(--fg); stroke-width: 2; }
.labapp .hatch { stroke: var(--muted); stroke-width: 1.2; }
.labapp .surf { fill: var(--panel2); stroke: var(--rampedge); stroke-width: 2; }
.labapp .ramp { fill: var(--ramp); stroke: var(--rampedge); stroke-width: 2; stroke-linejoin: round; }
.labapp .blk { fill: var(--block); stroke: var(--blockedge); stroke-width: 2; }
.labapp .blktxt { fill: var(--fg); font: italic 600 18px var(--math); }
.labapp .axis { stroke: var(--muted); stroke-width: 1.3; stroke-dasharray: 6 5; }
.labapp .axlab { fill: var(--muted); font: 500 16px var(--mono); }
.labapp .dot { fill: var(--fg); }
.labapp .mlab { font-family: var(--math); fill: var(--c); font-weight: 600; }
.labapp .arw line { stroke: var(--c); }
.labapp .arw polygon { fill: var(--c); }
.labapp .c-weight { --c: var(--weight); }
.labapp .c-normal { --c: var(--normal); }
.labapp .c-friction { --c: var(--friction); }
.labapp .c-applied { --c: var(--applied); }
.labapp .c-net { --c: var(--net); }
.labapp .c-vel { --c: var(--vel); }
.labapp .c-ok { --c: var(--ok); }
.labapp .c-bad { --c: var(--bad); }
.labapp .c-accent { --c: var(--accent); }
.labapp .arc { fill: none; stroke: var(--fg); stroke-width: 1.6; }
.labapp .arclab { fill: var(--fg); font: italic 20px var(--math); }
.labapp .ref-line { stroke: var(--muted); stroke-width: 1.3; stroke-dasharray: 5 5; }
.labapp .txt { fill: var(--fg); font-size: 15px; }
.labapp .txtm { fill: var(--muted); font-size: 14px; }
.labapp .mono { font-family: var(--mono) !important; }
.labapp .grid { stroke: var(--line); stroke-width: 1; }
.labapp .plotaxis { stroke: var(--fg); stroke-width: 1.6; }
.labapp .ticklab { fill: var(--muted); font: 13px var(--mono); }
.labapp .axtitle { fill: var(--fg); font-size: 15px; }
.labapp .curve { fill: none; stroke: var(--c); stroke-width: 3.2; stroke-linejoin: round; }
.labapp .curve.faint { stroke-width: 2; stroke-dasharray: 6 6; opacity: 0.55; }
.labapp .marker { fill: var(--bg); stroke: var(--fg); stroke-width: 3; }
.labapp .cable { stroke: var(--fg); stroke-width: 2.5; }
.labapp .rope { stroke: var(--blockedge); stroke-width: 3; }
.labapp .mount { fill: var(--panel2); stroke: var(--rampedge); stroke-width: 1.5; }
.labapp .sign { fill: var(--panel2); stroke: var(--fg); stroke-width: 2; }
.labapp .ball { fill: var(--block); stroke: var(--blockedge); stroke-width: 2; }
.labapp .strobe { fill: var(--accent); }
.labapp .cart { fill: var(--block); stroke: var(--blockedge); stroke-width: 2; }
.labapp .wheel { fill: var(--fg); }
.labapp .skater { fill: var(--panel2); stroke: var(--fg); stroke-width: 2; }
.labapp .car { fill: none; stroke: var(--fg); stroke-width: 2.2; }
.labapp .shaft { stroke: var(--line); stroke-width: 2; stroke-dasharray: 8 6; }
.labapp .placeholder { fill: var(--muted); font-size: 16px; }
@media (prefers-reduced-motion: reduce) { .labapp .bar .fill { transition: none; } }

/* fit the lab into the site page */
.labapp .tabbar { top: 0; margin: 18px 0 0; }
.labapp .labmain { padding-block: 22px 12px; }
.labapp h2 { font-family: var(--display); font-size: 1.5em; margin: 0; }
.labapp h3 { font-family: var(--display); font-size: 1.1em; margin: 0; }
.labapp [hidden] { display: none !important; }
.labapp p { margin: 0; max-width: none; color: var(--fg); }
.labapp li { color: var(--fg); margin: 0; }
.labapp table { margin: 0; width: 100%; font-size: 0.93em; }
.labapp th, .labapp td { color: var(--fg); }
.labapp svg.fig { margin: 0; max-width: none; }
.labapp .problem .q { border: 0; padding: 0; margin: 6px 0 0; border-radius: 0; }
.labapp details { margin: 0; }
.labapp .katex { font-size: 1.08em; }
.labapp .katex-display { margin: 0.3em 0; overflow-x: auto; overflow-y: hidden; }