@import"https://fonts.googleapis.com/css2?family=DM+Sans:wght@400;500;600;700&family=Newsreader:opsz,wght@6..72,400;6..72,500&display=swap";:root{font-family:DM Sans,PingFang SC,Microsoft YaHei,sans-serif;color:#292d28;background:#f7f3e9;font-synthesis:none;font-weight:400;line-height:1.6;--muted: #61665b;--line: #d6d5c8;--accent: #a3482c;--paper: #fffdf7}*{box-sizing:border-box}body{margin:0}button,a{-webkit-tap-highlight-color:transparent}button{font:inherit;color:inherit;cursor:pointer}button:disabled{cursor:default;opacity:.45}a{color:inherit;text-underline-offset:5px}button:focus-visible,a:focus-visible,summary:focus-visible{outline:3px solid #a3482c;outline-offset:5px}button[aria-pressed=true]:not(.memory-cell){background:#e8e9dc;border-color:#66725b}h1,h2,h3,p{margin:0}h1,h2{font-family:Newsreader,Songti SC,STSong,Georgia,serif;font-weight:400;line-height:1.1;letter-spacing:-.035em}button{border-radius:2px}h2:focus{outline:none}h2:focus-visible{outline:3px solid var(--accent);outline-offset:7px}.site-shell{max-width:1320px;padding:0 64px;margin:auto}.site-header{height:100px;display:flex;align-items:center;justify-content:space-between;border-bottom:1px solid var(--line)}.brand{text-decoration:none;font-weight:600;font-size:17px;display:flex;gap:12px;align-items:center}.brand-mark{font-family:Georgia,serif;background:#323e30;color:#fff;width:31px;height:34px;text-align:center;font-size:25px;line-height:29px}.languages{display:flex;align-items:center;gap:10px;font-size:13px}.languages button{background:none;border:0;padding:7px 10px;color:var(--muted)}.languages button[aria-pressed=true]{color:#292d28;border-bottom:1px solid #292d28;background:none}.languages span{color:#b3b4a8}.eyebrow,.mini-label{font-size:11px;font-weight:700;letter-spacing:.13em;color:var(--muted);text-transform:uppercase}.home{padding:72px 0 40px}.home h1{font-size:clamp(52px,6.5vw,83px);white-space:pre-line;margin:20px 0 22px;max-width:850px}.home-intro{max-width:530px;color:var(--muted);font-size:18px}.lesson-invitation{display:grid;grid-template-columns:1.2fr 1fr;border-top:1px solid var(--line);border-bottom:1px solid var(--line);margin:55px 0 24px;padding:36px 0;gap:30px}.invitation-copy h2{font-size:42px;white-space:pre-line;margin:17px 0}.invitation-copy>p:not(.eyebrow){max-width:470px;color:var(--muted)}.primary-link,.primary{display:inline-flex;align-items:center;justify-content:center;gap:35px;background:var(--accent);color:#fffdf7;border:1px solid var(--accent);padding:12px 23px;min-height:48px;font-weight:500;text-decoration:none;font-size:14px}.invitation-copy .primary-link{margin-top:24px}.home-illustration{position:relative;align-self:center;justify-self:center;width:240px;transform:rotate(-4deg)}.home-illustration .outside{display:block;font-size:19px;text-align:center;color:var(--accent);margin-bottom:12px}.home-illustration>div{font-family:Newsreader,Georgia,serif;font-size:92px;text-align:center;padding:26px 0;background:#edeedf;border:1px solid #9ca68d;box-shadow:8px 8px #e1e1d1}.small-note{display:block;text-align:right;color:var(--muted);font-size:12px;margin-top:20px}.home-note{font-size:14px;color:var(--muted)}.second-lesson,.third-lesson,.fourth-lesson{margin-top:24px}.bus-home-illustration{align-self:center;justify-self:center;display:grid;gap:8px;width:min(100%,320px)}.bus-home-illustration span{border:1px solid #7b8877;background:#eef0e6;padding:9px 14px;text-align:center;color:#3c5142;font-size:13px}.buses-lesson{padding-bottom:60px}.buses-heading{padding:58px 0 34px;max-width:790px}.buses-heading h1{font-size:clamp(42px,6vw,68px);margin:12px 0 16px}.buses-heading>p:last-child{color:var(--muted);font-size:18px}.bus-topology,.bus-explorer,.bus-check{border-top:1px solid var(--line);padding:28px 0}.bus-flow-diagram{display:grid;grid-template-columns:minmax(110px,.65fr) minmax(0,2.4fr) minmax(130px,.9fr);gap:10px;align-items:stretch}.bus-node{border:2px solid #ad754c;background:#fff0d9;text-align:center;padding:15px 10px;font-family:Newsreader,Georgia,serif;font-size:24px}.bus-cpu{align-self:center}.bus-endpoints{display:grid;grid-template-rows:1fr 1fr;gap:10px}.bus-group{position:relative;border:1px dashed #8c6595;padding:32px 12px 12px}.bus-group-label{position:absolute;top:3px;left:12px;color:#684775;font-size:12px;font-weight:700}.bus-lane{display:grid;grid-template-columns:minmax(145px,.8fr) minmax(160px,1fr) minmax(90px,.5fr);align-items:center;gap:12px;margin:7px 0;padding:12px 15px;border-left:5px solid #387698;background:#e9f0f2}.bus-lane strong{font-size:14px}.bus-lane>span{text-align:center;color:#365666;font-size:13px}.bus-lane small{text-align:right;color:var(--muted)}.bus-lane.active{outline:3px solid #a3482c;outline-offset:2px;font-weight:600}.data-lane{border-color:#50834b;background:#edf2e7}.data-lane>span{color:#41643d}.control-lane{border-color:#8a568e;background:#f1eaf2}.control-lane>span{color:#684775}.bus-roles{display:grid;grid-template-columns:repeat(3,1fr);gap:16px;margin-top:20px}.bus-roles p{color:var(--muted);font-size:14px}.bus-roles strong{display:block;color:#292d28;margin-bottom:5px}.cu-note{border-left:3px solid #8a568e;padding:9px 14px;margin-top:18px;background:#f1eaf2}.port-note{margin-top:16px;color:var(--muted);font-size:14px}.bus-explorer-heading{display:flex;justify-content:space-between;align-items:center;gap:20px}.bus-explorer h2{font-size:32px;margin-top:8px}.bus-mode{display:flex;gap:8px}.bus-mode button,.bus-predictions button{border:1px solid var(--line);background:var(--paper);padding:9px 16px}.bus-mode button[aria-pressed=true],.bus-predictions button[aria-pressed=true]{background:#e8e9dc;border-color:#66725b}.bus-example-state{display:grid;grid-template-columns:1fr 1fr;gap:14px;margin:22px 0}.bus-example-state>div{background:#fffdf7;border:1px solid var(--line);padding:13px 16px;display:grid;gap:4px}.bus-example-state span{color:var(--muted);font-size:12px}.bus-example-state strong{font-size:20px}.bus-try{border-left:3px solid #78836d;padding:12px 17px;background:#f0f1e8}.bus-try h3{font-size:12px;text-transform:uppercase;letter-spacing:.12em;margin-bottom:5px}.bus-predictions{display:flex;flex-wrap:wrap;gap:8px;margin-top:12px}.computer-event{display:flex;align-items:center;gap:18px;margin-top:22px;flex-wrap:wrap}.computer-event .eyebrow{min-width:120px}.event-output{flex:1;min-width:240px;padding:12px 16px;background:#eef0e6;border:1px solid #c4cbb9}.bus-check-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin-top:12px}.bus-check-grid p{display:grid;gap:4px;padding:12px;background:#fffdf7;border:1px solid var(--line)}.bus-check-grid strong{font-size:13px}.bus-check-grid span{color:#365666}.copy-home-illustration{align-self:center;justify-self:center;display:grid;grid-template-columns:1fr auto 1fr;align-items:center;gap:12px;width:min(100%,350px)}.copy-home-illustration>div{border:2px solid #78836d;background:var(--paper);padding:15px;display:flex;flex-direction:column;align-items:center;box-shadow:5px 5px #e1e1d1}.copy-home-illustration>span{font-size:10px;letter-spacing:.12em;color:var(--accent)}.copy-home-illustration small{color:var(--muted)}.copy-home-illustration strong{font-family:Newsreader,Georgia,serif;font-size:36px;font-weight:400}.processor-home-illustration{align-self:center;justify-self:center;width:min(100%,330px);border:2px solid #78836d;background:#f0f1e5;padding:20px;display:grid;grid-template-columns:1fr 1fr;gap:10px;box-shadow:8px 8px #e1e1d1}.processor-home-illustration>span{grid-column:1 / -1;color:var(--muted);font-size:12px;font-weight:700;letter-spacing:.1em;text-transform:uppercase}.processor-home-illustration>div{border:1px solid #b3b9a5;background:var(--paper);padding:12px;display:flex;flex-direction:column;gap:5px}.processor-home-illustration small{color:var(--muted)}.processor-home-illustration strong{font-family:Newsreader,Georgia,serif;font-size:34px;font-weight:400}.lesson-topline{display:flex;justify-content:space-between;align-items:center;margin:26px 0}.lesson-topline>a,.text-button{font-size:12px;color:var(--muted)}.lesson-topline>a{text-decoration:none}.text-button{border:0;background:none;padding:8px}.lesson-heading{display:flex;justify-content:space-between;align-items:center;margin:35px 0}.lesson-heading h1{font-size:clamp(34px,4vw,52px);margin:12px 0}.lesson-heading p:not(.eyebrow){color:var(--muted);font-size:15px}.lesson-number{font-family:Newsreader,Georgia,serif;font-size:95px;color:#c9cbba;line-height:1}.step-nav{display:grid;grid-template-columns:repeat(6,1fr);border-top:1px solid var(--line);border-bottom:1px solid var(--line)}.step-nav.processor-steps{grid-template-columns:repeat(4,1fr)}.step-nav button{background:none;border:0;border-bottom:3px solid transparent;display:flex;gap:10px;align-items:center;text-align:left;padding:17px 8px;font-size:11px;color:var(--muted)}.step-nav button[aria-current=step]{border-bottom-color:var(--accent);color:var(--accent)}.step-number{font-size:11px;letter-spacing:.05em}.workspace{display:grid;grid-template-columns:minmax(230px,.8fr) minmax(0,1.45fr);gap:55px;padding:50px 0 38px;align-items:start}.instruction h2{font-size:43px;margin:17px 0 21px;max-width:350px}.intro{color:var(--muted);font-size:15px;max-width:350px}.activity{background:var(--paper);border:1px solid var(--line);padding:24px 28px 28px;box-shadow:0 4px #eeeadf}.activity-top{display:flex;justify-content:space-between;align-items:center}.activity-top>span:last-child{font-family:Georgia;font-size:22px;color:#7d876e}.memory-cells{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px;margin:26px 0 0}.memory-cells.single{grid-template-columns:minmax(120px,155px);justify-content:center}.memory-cell{background:none;border:0;padding:0;min-width:0;text-align:center;opacity:1!important;-webkit-user-select:text;user-select:text}.address-label{display:flex;align-items:center;justify-content:center;gap:7px;font-size:10px;margin-bottom:10px;color:var(--muted);min-height:27px}.address-label strong{font-size:20px;font-weight:500;color:#34392f}.cell-compartment{min-height:138px;border:1px solid #b9bea8;background:#f0f1e5;display:flex;flex-direction:column;justify-content:center;position:relative}.contents-label{font-size:10px;letter-spacing:.06em;color:var(--muted)}.value{font-family:Newsreader,Georgia,serif;font-size:59px;line-height:1.15;font-weight:400;padding-top:6px}.concealed{visibility:hidden}.unrevealed{color:#b3b8a2}.memory-cell[aria-pressed=true] .cell-compartment{border:2px solid var(--accent);background:#f8ece0}.selection-note{display:block;height:30px;padding-top:7px;font-size:10px;color:var(--accent)}.model-caption{text-align:center;color:var(--muted);font-size:11px;margin:5px auto 24px;max-width:350px}.interaction{border-top:1px solid var(--line);padding-top:22px}.interaction h3{font-size:16px;line-height:1.6;font-weight:500;margin-bottom:15px}.interaction>.primary{margin-top:8px}.quiet{font-size:13px;color:var(--muted)}.choices{display:flex;gap:8px;flex-wrap:wrap;margin:10px 0}.choice{background:transparent;border:1px solid #c9cbbb;padding:9px 16px;min-width:54px;font-size:13px}.spoken{display:block;background:none;border:0;text-decoration:underline;text-underline-offset:4px;font-size:12px;color:var(--muted);padding:8px 0;margin-bottom:13px;text-align:left}.feedback{font-size:13px;line-height:1.7;border-left:2px solid #8d9879;padding:8px 0 8px 14px;margin-top:18px;color:#48513d}.readout{display:grid;grid-template-columns:1fr auto;gap:4px 15px;background:#eeeede;border:1px solid #cdd0b9;padding:16px;margin-top:20px}.readout>span{font-size:12px;align-self:center}.readout strong{font-family:Newsreader,Georgia,serif;font-size:36px;line-height:1}.readout small{grid-column:1/-1;font-size:10px;color:var(--muted)}.lesson-controls{border-top:1px solid var(--line);display:flex;justify-content:space-between;align-items:center;padding:24px 0}.lesson-controls>span{font-size:12px;color:var(--muted)}.secondary{padding:12px 23px;background:none;border:1px solid var(--line);min-height:48px;font-size:14px}.fresh-questions fieldset{padding:15px 0;border:0;border-bottom:1px solid var(--line);margin:8px 0}.fresh-questions fieldset:last-child{border:0}.fresh-questions legend{font-size:13px;font-weight:500;padding:0}.fresh-questions legend span{color:var(--accent)}.processor-workspace{grid-template-columns:minmax(230px,.75fr) minmax(0,1.55fr)}.computer-diagram{border:1px dashed #aeb3a2;background:#f6f4eb;margin:24px 0;padding:22px;display:grid;grid-template-columns:1fr 1fr;gap:18px}.computer-diagram.reversed .processor-box{order:-1}.component-box{min-width:0;border:1px solid #b9bea8;padding:18px;background:var(--paper)}.component-box h4{font-size:16px;margin:0 0 2px}.component-box>p{color:var(--muted);font-size:11px;margin:0 0 15px}.processor-box{border:2px solid #78836d;background:#eef0e4}.processor-placeholder{min-height:115px;display:grid;place-items:center;color:#9ba28f;font-size:30px;letter-spacing:.3em}.mini-memory,.registers{display:grid;gap:9px}.mini-memory{grid-template-columns:repeat(3,minmax(0,1fr))}.registers{grid-template-columns:repeat(2,minmax(0,1fr))}.mini-memory-cell,.register-box{border:1px solid #c3c6b7;background:#f2f2e8;min-width:0;min-height:104px;padding:10px;display:flex;flex-direction:column;align-items:center;justify-content:center}.mini-memory-cell span,.mini-memory-cell small,.register-box span{color:var(--muted);font-size:10px;text-align:center}.mini-memory-cell strong,.register-box strong{font-family:Newsreader,Georgia,serif;font-weight:400;font-size:39px;line-height:1.15}.register-box{background:var(--paper);border:1px solid #8f9980}.question-group{border:0;border-bottom:1px solid var(--line);margin:0;padding:16px 0}.question-group:last-child{border-bottom:0}.question-group legend{font-size:13px;font-weight:600;padding:0}.question-group>p:not(.feedback){color:var(--muted);font-size:12px;margin-top:5px}.copy-computer{border:1px dashed #aeb3a2;background:#f6f4eb;margin:24px 0;padding:18px}.copy-processor,.copy-memory{border:2px solid #78836d;background:#eef0e4;padding:16px;min-width:0}.copy-processor h3,.copy-processor h4,.copy-memory h3,.copy-memory h4{margin:0 0 12px;font-size:13px;letter-spacing:.08em;text-transform:uppercase}.copy-registers,.copy-memory-cells{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:10px}.copy-memory-cells{grid-template-columns:repeat(3,minmax(0,1fr))}.copy-location{position:relative;min-width:0;min-height:105px;padding:20px 10px 10px;border:2px solid #7b866f;background:var(--paper);display:flex;flex-direction:column;align-items:center;justify-content:center;-webkit-user-select:text;user-select:text}.copy-location.destination-location{border-style:dashed;border-color:var(--accent)}.copy-location.source-location{border-width:3px}.copy-location>span,.copy-location>small:not(.location-role){color:var(--muted);font-size:10px;text-align:center}.copy-location>strong{font-family:Newsreader,Georgia,serif;font-size:40px;line-height:1.1;font-weight:400}.location-role{position:absolute;top:0;left:0;padding:3px 7px;background:#66725b;color:#fff;font-size:9px;font-weight:700;letter-spacing:.08em;text-transform:uppercase}.destination-location .location-role{background:var(--accent)}.copy-cue{margin:0 0 18px;padding:10px 13px;border-left:3px solid var(--accent);background:#f5eee5;color:#633523;font-size:13px;font-weight:600}.result-cue{margin-top:22px}.copy-comparison{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px;align-items:start}.copy-comparison>.copy-computer{margin:0}.result-computer{background:#f2f0e2;box-shadow:5px 5px #e1e1d1}.memory-copy-layout{display:grid;grid-template-columns:minmax(0,1.35fr) minmax(130px,.65fr);gap:14px}.memory-copy-layout .copy-registers,.memory-comparison{grid-template-columns:1fr}.route-note{margin-top:16px;color:var(--muted);font-size:12px}.fresh-copy-grid{display:grid;gap:28px;margin-top:16px}.fresh-copy-example{border-top:1px solid var(--line);padding-top:20px}.fresh-copy-example>h3{font-family:Newsreader,Georgia,serif;font-size:27px}.choice[aria-disabled=true],.spoken[aria-disabled=true]{cursor:default;opacity:.72}.reveal-note{margin:14px 0}.ending{padding:20px 0}.ending h2{font-size:32px}.ending p{font-size:14px;color:var(--muted);margin-top:10px}footer{display:flex;justify-content:space-between;padding:22px 0 35px;color:var(--muted);font-size:11px}.skip-link{position:absolute;top:-100px;background:var(--paper);padding:10px;z-index:10}.skip-link:focus{top:10px}.updated{animation:replace .4s ease-out}@keyframes replace{0%{opacity:.25;transform:translateY(5px)}to{opacity:1;transform:translateY(0)}}@media(min-width:1500px){.site-shell{padding:0 40px}}@media(max-width:900px){.site-shell{padding:0 30px}.workspace{gap:28px;grid-template-columns:minmax(200px,.75fr) minmax(0,1.25fr)}.activity{padding:20px}.step-name{font-size:10px}.step-nav button{gap:5px}.instruction h2{font-size:35px}.memory-cells{gap:10px}.computer-diagram{padding:14px;gap:12px}.address-label{flex-wrap:wrap;gap:2px 5px}.value{font-size:49px}}@media(max-width:650px){.site-shell{padding:0 20px}.site-header{height:79px}.brand{font-size:13px;gap:8px}.brand-mark{width:25px;height:29px;font-size:21px}.languages{gap:3px;font-size:12px}.languages button{padding:5px}.lesson-heading{margin:26px 0}.lesson-heading h1{font-size:34px}.lesson-number{display:none}.step-nav button{justify-content:center;padding:13px 4px}.step-name{display:none}.step-number{font-size:12px}.workspace{grid-template-columns:1fr;gap:24px;padding:28px 0}.copy-comparison,.memory-copy-layout{grid-template-columns:1fr}.copy-memory-cells{gap:6px}.copy-location{min-height:92px;padding-inline:6px}.instruction h2{font-size:36px;max-width:none;margin:12px 0 15px}.intro{max-width:none}.activity{padding:20px 16px}.cell-compartment{min-height:115px}.value{font-size:48px}.address-label{font-size:9px}.address-label strong{font-size:18px}.memory-cells{gap:9px}.computer-diagram{grid-template-columns:1fr}.computer-diagram.reversed .processor-box{order:0}.component-box{padding:14px}.home{padding-top:45px}.home h1{font-size:53px}.home-intro{font-size:16px}.lesson-invitation{grid-template-columns:1fr;margin-top:36px;padding:28px 0}.home-illustration{width:180px;margin:20px 0}.bus-flow-diagram{grid-template-columns:1fr}.bus-cpu{min-height:55px}.bus-endpoints{grid-template-columns:1fr 1fr;grid-template-rows:1fr}.bus-lane{grid-template-columns:1fr;gap:3px}.bus-lane>span,.bus-lane small{text-align:left}.bus-roles,.bus-check-grid{grid-template-columns:1fr}.bus-explorer-heading{align-items:flex-start;flex-direction:column}.bus-example-state{grid-template-columns:1fr}.computer-event{align-items:stretch;flex-direction:column;gap:10px}.home-illustration>div{font-size:75px}.invitation-copy h2{font-size:38px}footer{gap:20px;font-size:10px}.lesson-controls .primary-link{padding:12px 16px;font-size:12px}}@media(prefers-reduced-motion:reduce){.copy-location,.copy-computer,.result-computer{animation:none!important;transition:none!important}}@media(prefers-reduced-motion:reduce){*,*:before,*:after{animation:none!important;transition:none!important;scroll-behavior:auto!important}}