._lesson_3du1h_1{--ink:var(--foreground);--muted:var(--muted-foreground);--line:var(--border);--paper:var(--card);--plot:var(--card);--motion:#187e91;--blue:var(--motion);--force:#aa612a;--return:#9464a4;max-width:1120px;color:var(--ink);padding-bottom:72px}.dark ._lesson_3du1h_1{--motion:#68c8d5;--force:#e8ac71;--return:#d4a5e3}._header_3du1h_20{padding:48px 0 24px}._eyebrow_3du1h_23{color:var(--force);font:12px var(--font-mono,monospace);letter-spacing:.12em}._header_3du1h_20 h1{font:400 clamp(34px, 5vw, 60px)/1.18 var(--font-serif,Georgia, serif);letter-spacing:-.025em;margin:16px 0 28px}._prose_3du1h_33{max-width:900px;color:var(--muted);margin:20px 0;font-size:16px;line-height:1.95}._nav_3du1h_40{border-block:1px solid var(--line);flex-wrap:wrap;gap:15px 27px;padding:20px 0;font-size:13px;display:flex}._nav_3du1h_40 a{color:var(--muted)}._nav_3du1h_40 a:hover{color:var(--ink);text-underline-offset:5px;text-decoration:underline}._section_3du1h_56{margin-top:66px;scroll-margin-top:110px}._section_3du1h_56 h2{font:400 clamp(25px, 3vw, 36px)/1.4 var(--font-serif,Georgia, serif);align-items:baseline;gap:18px;display:flex}._section_3du1h_56 h2 small{font:12px var(--font-mono,monospace);color:var(--force)}._section_3du1h_56 h3{font:400 25px/1.4 var(--font-serif,Georgia, serif);margin:42px 0 20px}._experiment_3du1h_74{border:1px solid var(--line);background:var(--paper);border-radius:12px;margin:28px 0;overflow:hidden}._experimentHead_3du1h_81{border-bottom:1px solid var(--line);flex-wrap:wrap;justify-content:space-between;align-items:center;gap:12px;padding:18px 24px;display:flex}._experimentHead_3du1h_81 strong{font-size:15px;font-weight:500}._experimentHead_3du1h_81 span{font:13px var(--font-mono,monospace);color:var(--muted)}._lane_3du1h_98{padding:20px 24px 12px}._lane_3du1h_98+._lane_3du1h_98{border-top:1px solid var(--line)}._laneHead_3du1h_104{flex-wrap:wrap;justify-content:space-between;align-items:baseline;gap:8px 20px;display:flex}._laneHead_3du1h_104 strong{font-size:15px;font-weight:500}._laneHead_3du1h_104 span{color:var(--muted);font-size:12px}._readouts_3du1h_119{grid-template-columns:repeat(3,minmax(0,1fr));gap:15px;padding-top:6px;display:grid}._readout_3du1h_119 small{color:var(--muted);margin-bottom:5px;font-size:12px;display:block}._readout_3du1h_119 strong{font:500 17px/1.5 var(--font-mono,monospace)}._readout_3du1h_119[data-kind=velocity] strong{color:var(--motion)}._readout_3du1h_119[data-kind=force] strong{color:var(--force)}._controls_3du1h_140{border-top:1px solid var(--line);padding:20px 24px}._controls_3du1h_140 input{width:100%;accent-color:var(--motion)}._choices_3du1h_148{flex-wrap:wrap;gap:8px;margin:16px 0;display:flex}._choices_3du1h_148 button{border:1px solid var(--line);background:var(--paper);color:var(--muted);border-radius:6px;padding:10px 13px;font-size:13px;line-height:1.5}._choices_3du1h_148 button[aria-pressed=true]{color:var(--ink);border-color:var(--motion);background:color-mix(in srgb, var(--motion) 9%, var(--paper))}._choices_3du1h_148 button:hover{color:var(--ink);border-color:var(--motion)}._caption_3du1h_172{color:var(--muted);border-top:1px solid var(--line);margin:0;padding:16px 24px;font-size:14px;line-height:1.8}._law_3du1h_180{border-left:3px solid var(--motion);margin:30px 0;padding:3px 0 3px 24px}._law_3du1h_180 ._prose_3du1h_33{color:var(--ink)}._equation_3du1h_188{margin:16px 0;padding:8px 14px;font-size:18px;overflow-x:auto}._spaceWrap_3du1h_194{border-block:1px solid var(--line);background:#edece6;position:relative}._space_3du1h_194{width:100%;height:470px}._space_3du1h_194 canvas{touch-action:pan-y;width:100%;height:100%;display:block}._space_3du1h_194 canvas:focus-visible{outline:2px solid var(--motion);outline-offset:-4px}._spaceWrap_3du1h_194[data-model-kind=wall] ._space_3du1h_194,._spaceWrap_3du1h_194[data-model-kind=block] ._space_3du1h_194{height:480px}._spaceWrap_3du1h_194[data-model-kind=balance] ._space_3du1h_194{height:340px}._cameraControls_3du1h_220{gap:6px;display:flex;position:absolute;bottom:14px;right:16px}._cameraControls_3du1h_220 button{color:#34434a;cursor:pointer;background:#fffaf0e8;border:1px solid #c7c5ba;border-radius:50%;place-items:center;width:36px;height:36px;display:grid}._cameraControls_3du1h_220 button:hover{background:#fff}._modelStatus_3du1h_241{color:#46595e;background:#edece6;place-content:center;gap:15px;font-size:14px;display:grid;position:absolute;inset:0}._modelStatus_3du1h_241 button{border:1px solid;border-radius:5px;padding:8px 14px}._laneGrid_3du1h_256{grid-template-columns:repeat(3,minmax(0,1fr));display:grid}._laneGrid_3du1h_256._twoLanes_3du1h_260{grid-template-columns:repeat(2,minmax(0,1fr))}._laneGrid_3du1h_256 ._lane_3du1h_98{padding:22px 20px}._laneGrid_3du1h_256 ._lane_3du1h_98+._lane_3du1h_98{border-top:0;border-left:1px solid var(--line)}._laneHead_3du1h_104 small{font:11px var(--font-mono,monospace);color:var(--force);margin-right:8px}._laneGrid_3du1h_256 ._laneHead_3du1h_104{align-content:start;min-height:60px}._laneGrid_3du1h_256 ._readouts_3du1h_119{grid-template-columns:1fr;gap:7px}._laneGrid_3du1h_256 ._readout_3du1h_119{justify-content:space-between;align-items:baseline;gap:8px;display:flex}._laneGrid_3du1h_256 ._readout_3du1h_119 strong{font-size:15px}._forceCards_3du1h_292{grid-template-columns:repeat(2,minmax(0,1fr));gap:20px;padding:20px 24px;display:grid}._forceCard_3du1h_292{color:#b75a22;justify-content:space-between;align-items:center;gap:10px;min-width:0;display:flex}._forceCard_3du1h_292[data-force-index="1"]{color:#8560ad}.dark ._forceCard_3du1h_292{color:#efae73}.dark ._forceCard_3du1h_292[data-force-index="1"]{color:#c4a1e8}._forceCard_3du1h_292>strong{align-items:center;gap:10px;font-size:14px;font-weight:500;display:flex}._forceCard_3du1h_292 i{background:currentColor;border-radius:50%;flex:none;width:8px;height:8px}._forceCard_3du1h_292 output{font:16px var(--font-mono,monospace);white-space:nowrap}._contactLegend_3du1h_333{color:var(--muted);justify-content:space-around;padding:10px 20px 18px;font-size:13px;display:flex}._balanceEquation_3du1h_340{text-align:center;padding:0 20px 20px}._collisionReadouts_3du1h_344{padding:0 24px 20px}._checks_3du1h_347{gap:20px;margin:28px 0;display:grid}._check_3du1h_347{border-bottom:1px solid var(--line);padding-bottom:20px}._check_3du1h_347>p{margin:0 0 12px;line-height:1.8}._check_3du1h_347 summary{cursor:pointer;color:var(--motion);font-size:14px}._check_3du1h_347 details p{color:var(--muted);margin:12px 0 0;line-height:1.85}._sources_3du1h_370{color:var(--muted);flex-wrap:wrap;gap:12px 25px;margin:20px 0;font-size:13px;display:flex}._sources_3du1h_370 a{text-underline-offset:4px;text-decoration:underline}._next_3du1h_382{color:var(--motion);align-items:center;gap:15px;padding:20px 0;display:inline-flex}@media (max-width:600px){._header_3du1h_20{padding-top:30px}._section_3du1h_56{margin-top:48px}._prose_3du1h_33{font-size:15px;line-height:1.95}._lane_3du1h_98,._controls_3du1h_140,._experimentHead_3du1h_81{padding:16px 14px}._caption_3du1h_172{padding:14px}._readouts_3du1h_119{gap:8px}._readout_3du1h_119 strong{font-size:14px}._readout_3du1h_119 small{font-size:11px}._forceCards_3du1h_292{gap:10px;padding:16px 12px}._forceCard_3du1h_292{flex-direction:column;align-items:start;gap:8px}._forceCard_3du1h_292>strong{font-size:13px}._space_3du1h_194{height:210px}._spaceWrap_3du1h_194[data-model-kind=wall] ._space_3du1h_194,._spaceWrap_3du1h_194[data-model-kind=block] ._space_3du1h_194{height:300px}._spaceWrap_3du1h_194[data-model-kind=friction] ._space_3du1h_194{height:240px}._spaceWrap_3du1h_194[data-model-kind=balance] ._space_3du1h_194{height:190px}._laneGrid_3du1h_256,._laneGrid_3du1h_256._twoLanes_3du1h_260{grid-template-columns:1fr}._laneGrid_3du1h_256 ._lane_3du1h_98{padding:15px 14px}._laneGrid_3du1h_256 ._lane_3du1h_98+._lane_3du1h_98{border-left:0;border-top:1px solid var(--line)}._laneGrid_3du1h_256 ._laneHead_3du1h_104{min-height:0}._laneGrid_3du1h_256 ._readouts_3du1h_119{grid-template-columns:repeat(3,minmax(0,1fr));gap:9px;margin-top:8px;display:grid}._laneGrid_3du1h_256 ._readout_3du1h_119{display:block}._laneGrid_3du1h_256 ._readout_3du1h_119 strong{font-size:13px}._twoLanes_3du1h_260 ._readout_3du1h_119:last-child strong{white-space:nowrap;font-size:clamp(10px,3vw,12px)}._cameraControls_3du1h_220{bottom:10px;right:10px}._collisionReadouts_3du1h_344{padding:0 14px 16px}._law_3du1h_180{padding-left:16px}._equation_3du1h_188{padding-inline:2px;font-size:16px}}