*{box-sizing:border-box}html{color-scheme:light;background:#f4f1e8;-webkit-text-size-adjust:100%}body{margin:0;color:#233d38;font-family:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif}button,select{font:inherit}button,a,select{-webkit-tap-highlight-color:transparent}button{cursor:pointer}button,select{min-height:44px;border:1px solid #cad4c7;background:#fffdf6;color:#233d38;border-radius:10px;padding:9px 14px;font-weight:650}button:hover:not(:disabled){background:#e4eee3}button:disabled{opacity:.43;cursor:default}button:focus-visible,a:focus-visible,select:focus-visible,canvas:focus-visible{outline:3px solid #ae500f;outline-offset:3px}button[aria-pressed=true]{background:#d9e8d7;border-color:#42745b;color:#234c3c}a{color:inherit}header{max-width:1280px;margin:auto;padding:15px 28px;border-bottom:1px solid #d8dccf;display:flex;justify-content:space-between;align-items:center;gap:12px}.brand{font-size:16px;font-weight:850;text-decoration:none;letter-spacing:-.5px}.brand span{color:#a45122}nav{display:flex;gap:22px;align-items:center;font-size:13px}nav a{text-decoration:none}main{width:min(1100px,calc(100% - 48px));margin:auto}.intro{display:flex;justify-content:space-between;align-items:center;padding:28px 0 22px}.eyebrow{font-size:10px;font-weight:800;letter-spacing:1.9px;color:#647366;margin:0 0 11px}h1{font-family:Georgia,serif;font-size:48px;letter-spacing:-1.8px;line-height:1;margin:0}h1 em{font-weight:400;color:#bd623f}.intro-copy{color:#667363;font-size:14px;line-height:1.7;margin:0}.workspace{display:grid;grid-template-columns:minmax(0,710px) minmax(250px,310px);gap:36px;align-items:start}.play{min-width:0}.level-bar{display:flex;gap:12px;align-items:center;padding:0 0 12px}.level-bar>label{font-size:11px;text-transform:uppercase;letter-spacing:1px;font-weight:750;white-space:nowrap}.level-bar select{min-width:0;flex:1;font-size:14px;background:#faf9f2}.progress{font-size:12px;color:#5d705f;white-space:nowrap}.drawing-tools{display:flex;gap:6px;margin-bottom:10px;flex-wrap:wrap}.drawing-tools button{font-size:13px;padding:8px 12px}.drawing-tools #clear{margin-left:auto}.board-wrap{position:relative;overflow:hidden;border:1px solid #cbd2c3;border-radius:14px;box-shadow:0 7px 24px #38482c0b;background:#fffdf6;max-width:600px;margin:auto}canvas{width:100%;display:block;aspect-ratio:5/6;touch-action:none;cursor:crosshair}.paper-label{position:absolute;top:14px;left:20px;right:20px;display:flex;justify-content:space-between;pointer-events:none;font-size:8px;letter-spacing:2px;color:#7b8976}.actions{display:flex;gap:8px;margin-top:12px}.actions button{font-size:13px}.actions .primary{flex:1}.primary{background:#275a45;color:#fffdf1;border-color:#275a45}.primary:hover:not(:disabled){background:#1c4836}.quiet{border-color:transparent;background:transparent}.status{min-height:36px;font-size:13px;line-height:1.5;margin:11px 2px;color:#536652}.note{padding:24px;border:1px solid #d3dacd;background:#fcfaf2;border-radius:14px;margin-bottom:17px}h2{font-family:Georgia,serif;font-size:25px;font-weight:500;line-height:1.2;letter-spacing:-.5px;margin:0 0 14px}.note p,.lab-invite p{font-size:14px;line-height:1.7;margin:0 0 18px}.note .eyebrow,.instruments .eyebrow{font-size:9px;margin-bottom:13px}.note .small,.small{font-size:11px;line-height:1.7;color:#61705d;margin:15px 0 0}.text-button{display:flex;justify-content:space-between;align-items:center;gap:25px;width:100%;border:0;border-bottom:1px solid #c6d3bf;border-radius:0;padding:8px 0;text-align:left;background:transparent;font-size:13px}.text-button[aria-pressed=true]{background:transparent}.instruments{padding:22px 24px;background:#e8eddf;border-radius:14px;margin-bottom:17px}.readouts{display:flex;gap:30px;border-bottom:1px solid #c6d1bf;padding-bottom:17px;margin-bottom:16px}.readouts strong{font-size:32px;font-weight:550;letter-spacing:-1px;font-variant-numeric:tabular-nums}.readouts span{display:block;color:#607259;font-size:9px}.fact{display:flex;justify-content:space-between;gap:10px;font-size:11px;margin-top:13px}.fact strong{font-weight:650}.lab-invite{padding:12px 24px}.lab-invite h2{font-size:23px;max-width:180px;margin-top:10px}.lab-invite p{font-size:13px;color:#687460}.lab-invite button{font-size:12px;background:#f0e6d3;border-color:#d9caac}.orbit{display:block;color:#b16b45;font-size:35px}.note label{display:block;font-size:12px;font-weight:650;margin:16px 0}.note select{display:block;width:100%;font-size:13px;margin-top:6px}.result{position:absolute;left:10%;right:10%;top:27%;padding:27px;text-align:center;background:#fffef4f5;border:1px solid #ced9c8;border-radius:16px;box-shadow:0 10px 60px #17342225;backdrop-filter:blur(8px)}.result p{font-size:13px;line-height:1.6}.result button{display:block;margin:12px auto 0;width:100%}.result-mark{display:grid;place-items:center;margin:0 auto 16px;background:#e1edda;color:#2b6044;border-radius:100%;width:40px;height:40px;font-size:23px}.result h2{font-size:28px}footer{border-top:1px solid #d4dbcd;padding:17px 0 25px;color:#71806d;font-size:11px;line-height:1.8}footer p{margin:4px 0}dialog{border:1px solid #cdd6c7;border-radius:20px;background:#fffdf5;color:#294435;max-width:min(620px,calc(100% - 28px));max-height:85dvh;padding:32px;box-shadow:0 16px 80px #001b2144}dialog::backdrop{background:#163d3b88;backdrop-filter:blur(4px)}dialog h3{font-size:15px;margin-top:24px}dialog p,dialog li{font-size:14px;line-height:1.8}dialog li{margin:12px 0}dialog ol{padding-left:23px}.close{float:right;font-size:25px;line-height:1;margin:-14px -14px 10px 10px}.dialog-actions{display:flex;gap:10px}.warning{color:#9b461c!important}[hidden]{display:none!important}@media(min-width:1000px) and (max-height:940px){.board-wrap{max-width:480px}.intro{padding:21px 0 20px}.workspace{grid-template-columns:minmax(0,650px) 290px;gap:32px}main{max-width:1000px}.lab-invite{padding-top:0}.lab-invite .orbit{display:none}}@media(max-width:760px){header{padding:8px 14px;min-height:54px}nav{gap:14px;font-size:12px}.brand{font-size:13px}nav button{font-size:12px;padding:8px}.intro{padding:21px 0 18px}.intro-copy{display:none}h1{font-size:36px}.eyebrow{font-size:8px;letter-spacing:1.6px;margin-bottom:9px}main{width:calc(100% - 24px)}.workspace{display:block}.level-bar{gap:8px;padding-bottom:9px}.level-bar>label{display:none}.level-bar select{font-size:13px}.drawing-tools{gap:5px;margin-bottom:9px}.drawing-tools button{font-size:12px;padding:8px 10px;flex:1}.drawing-tools #clear{margin:0}.board-wrap{border-radius:12px}.paper-label{font-size:7px;top:10px;left:12px;right:12px}.actions{gap:6px}.actions button{padding:9px 10px;font-size:12px}.status{font-size:12px;min-height:32px;margin:9px 0 14px}aside{display:grid;grid-template-columns:1fr;gap:14px}.note,.instruments{padding:20px;margin:0}.lab-invite{padding:15px 20px}.lab-invite h2{max-width:none}.lab-invite .orbit{display:none}footer{margin-top:20px}.result{top:24%;padding:20px;left:7%;right:7%}.result h2{font-size:25px}dialog{padding:24px}.drawing-tools:has(#move:not([hidden])) #clear{flex:0} .drawing-tools #move{flex:0 0 100%}}
@media(min-width:761px){.board-wrap{max-width:clamp(320px,calc((100dvh - 365px) * .833333),600px)}}
.focus-button{font-size:11px;padding:8px 10px;white-space:nowrap}.drawing-tools button{white-space:nowrap}.focus-mode header,.focus-mode .intro,.focus-mode aside,.focus-mode footer{display:none}.focus-mode main{max-width:850px;width:calc(100% - 20px);padding-top:10px}.focus-mode .workspace{display:block}.focus-mode .board-wrap{max-width:min(calc(100vw - 24px),max(200px,calc((100dvh - 205px) * .833333)))}.focus-mode .status{text-align:center}.focus-mode .drawing-tools{flex-wrap:nowrap}.focus-mode .drawing-tools #move{flex:0 1 auto}.focus-mode .level-bar>label{display:none}@media(max-width:760px){.drawing-tools button{padding:8px 6px;font-size:11px}.focus-button{font-size:10px;padding:8px}.level-bar{gap:6px}.level-bar select{padding-left:9px;font-size:12px}.focus-mode .drawing-tools #move{font-size:10px}.focus-mode .drawing-tools{gap:3px}}
.focus-mode header{display:flex;max-width:870px;padding:4px 10px;min-height:52px}.focus-mode .board-wrap{max-width:min(calc(100vw - 24px),max(140px,calc((100dvh - 265px) * .833333)))}
/* Activity896: give the sketchbook the viewport; put desktop controls beside it. */
#star-book{display:grid;grid-template-columns:repeat(3,1fr);gap:6px}#star-book button{font-size:11px;padding:8px 5px;white-space:nowrap;color:#775316}#star-book button[aria-current=true]{border-color:#548466;background:#e8efdf}.star-book .small{font-size:10px}.star-book{padding:16px!important}
@media(min-width:1000px){body:not(.focus-mode) header{max-width:1320px;padding:8px 22px;min-height:60px}body:not(.focus-mode) main{width:min(1280px,calc(100% - 36px));max-width:1280px}body:not(.focus-mode) .intro{padding:14px 0 16px}body:not(.focus-mode) .intro .eyebrow{display:none}body:not(.focus-mode) h1{font-size:34px}body:not(.focus-mode) .intro-copy{font-size:12px;line-height:1.4}body:not(.focus-mode) .workspace{display:grid;grid-template-columns:minmax(0,1fr) 280px;gap:0 24px;grid-template-rows:auto auto auto auto 1fr;align-items:start}body:not(.focus-mode) .play{display:contents}body:not(.focus-mode) .board-wrap{grid-column:1;grid-row:1 / 6;align-self:start;position:sticky;top:12px;max-width:none;width:min(100%,max(500px,calc((100dvh - 140px) * .833333)));margin:0 auto}body:not(.focus-mode) .level-bar{grid-column:2;grid-row:1;flex-wrap:wrap;padding:0 0 10px;gap:6px}body:not(.focus-mode) .level-bar>label{display:none}body:not(.focus-mode) .level-bar select{width:100%;flex:1 1 100%;font-size:12px}body:not(.focus-mode) .level-bar .progress{margin-right:auto}body:not(.focus-mode) .drawing-tools{grid-column:2;grid-row:2;gap:5px}body:not(.focus-mode) .drawing-tools button{padding:8px 9px;font-size:12px;flex:1}body:not(.focus-mode) .drawing-tools #clear{margin:0}body:not(.focus-mode) .actions{grid-column:2;grid-row:3;display:grid;grid-template-columns:1fr 1fr;margin:0;gap:6px}body:not(.focus-mode) .actions #release{grid-column:1 / 3}body:not(.focus-mode) .status{grid-column:2;grid-row:4;font-size:12px;margin:9px 0 13px;min-height:34px}body:not(.focus-mode) aside{grid-column:2;grid-row:5;display:flex;flex-direction:column;gap:12px}body:not(.focus-mode) .note,body:not(.focus-mode) .instruments{padding:16px;margin:0}body:not(.focus-mode) .note h2{font-size:22px}body:not(.focus-mode) .note p{font-size:12px;margin-bottom:10px}body:not(.focus-mode) .note .small{font-size:10px;margin-top:10px}body:not(.focus-mode) .lab-invite{padding:8px 16px}body:not(.focus-mode) .lab-invite .orbit{display:none}body:not(.focus-mode) .instruments .readouts{padding-bottom:12px;margin-bottom:12px}body:not(.focus-mode) .readouts strong{font-size:26px}body:not(.focus-mode) footer{margin-top:20px}}
@media(max-width:760px){body:not(.focus-mode) main{width:calc(100% - 12px)}body:not(.focus-mode) .intro{padding:14px 6px}body:not(.focus-mode) .intro .eyebrow{display:none}body:not(.focus-mode) h1{font-size:29px}body:not(.focus-mode) .level-bar,body:not(.focus-mode) .drawing-tools,body:not(.focus-mode) .actions{margin-left:3px;margin-right:3px}.star-book{margin-top:0}}
/* Activity1000: material choices and two-stage physics controls. */
.materials{flex:0 0 100%;display:grid;grid-template-columns:auto 1fr;align-items:center;gap:6px 10px;padding:10px;background:#ebece1;border:1px solid #ccd5c4;border-radius:11px}.materials label{font-size:11px;font-weight:750}.materials select{min-width:0;font-size:12px;padding:8px}.materials p{grid-column:1/-1;font-size:11px;line-height:1.4;margin:0;color:#576b57}.challenge-meta{display:flex;gap:8px;justify-content:space-between;flex-wrap:wrap;margin-bottom:13px;font-size:10px}.challenge-meta span{color:#a34d1d;letter-spacing:1px;font-weight:800}.challenge-meta strong{font-weight:600}.actions{flex-wrap:wrap}#drop-drawing{background:#fff0d5;border-color:#be8a42;color:#724516}#release{white-space:nowrap}.focus-mode .drawing-tools{flex-wrap:wrap}.focus-mode .materials{padding:5px 10px}.focus-mode .materials p{display:none}.focus-mode .board-wrap{max-width:min(calc(100vw - 24px),max(140px,calc((100dvh - 340px) * .833333)))}
@media(min-width:1000px){body:not(.focus-mode) .actions #drop-drawing{grid-column:1/3}body:not(.focus-mode) .materials select{padding:8px 5px}}
@media(max-width:760px){.materials{padding:7px 10px}.actions #drop-drawing,.actions #release{flex:1 1 45%}.actions #reset,.actions #pause,.actions #slow{flex:1}.materials select{font-size:12px}.paper-label{font-size:6px}}
.materials .challenge-meta{grid-column:1/-1;margin:0 0 3px}.focus-mode .materials .challenge-meta{display:none}
button,select{touch-action:manipulation}
/* Activity 1014: an illustrated, openly selectable 32-level challenge book. */
.in-book main{width:min(1320px,calc(100% - 48px))!important;max-width:1320px!important}.in-book .intro{border-bottom:1px solid #d1d8c9;margin-bottom:30px}.book-heading{display:flex;justify-content:space-between;align-items:center;gap:24px;margin:0 0 24px}.book-heading h2{font-size:40px;margin:0 0 10px}.book-heading p:not(.eyebrow){font-size:14px;line-height:1.6;margin:0;color:#61715e}.book-total{text-align:right;flex-shrink:0}.book-total>strong{display:block;font:40px Georgia,serif;color:#a16a23}.book-total strong span{font-size:24px;color:#74826d}.book-total>span{display:block;font-size:9px;letter-spacing:1.7px;font-weight:800;margin:5px 0}.book-total p{font-size:12px!important}.book-toolbar{display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap}#level-filters{display:flex;gap:6px;flex-wrap:wrap}#level-filters button{font-size:12px;padding:8px 13px;border-radius:24px;background:transparent}#level-filters button[aria-pressed=true]{background:#2d5541;color:#fffdf2;border-color:#2d5541}#resume-level{font-size:12px}.book-legend{display:flex;align-items:center;gap:20px;flex-wrap:wrap;font-size:11px;color:#62745c;margin:22px 0 0}.book-legend span{display:flex;align-items:center;gap:7px}.legend-ball{display:inline-block;width:10px;height:10px;border-radius:50%;background:#d97753}.legend-cup{display:inline-block;width:14px;height:12px;border:2px solid #346547;border-top:0}#gallery-count{margin:12px 0 14px}.level-grid{display:grid;grid-template-columns:repeat(8,minmax(0,1fr));gap:13px}.level-card{display:flex;flex-direction:column;align-items:stretch;padding:0;overflow:hidden;text-align:left;background:#fffdf6;border-color:#d2d8c9;border-radius:12px;box-shadow:0 3px 0 #d8ddce;transition:transform .16s,box-shadow .16s;min-width:0}.level-card:hover:not(:disabled){transform:translateY(-3px);box-shadow:0 6px 14px #2f4d3420;background:#fffdf6}.level-card[aria-current=true]{outline:2px solid #42694a;outline-offset:2px}.card-top{display:flex;align-items:center;justify-content:space-between;padding:8px 9px;gap:5px}.card-number{font:700 20px Georgia,serif;color:#38553b}.card-difficulty{font-size:8px;letter-spacing:.6px;color:#956127;white-space:nowrap}.level-preview{height:137px;display:block;background:#eaf0e3;border-top:1px solid #e2e7da;border-bottom:1px solid #e2e7da}.level-preview svg{width:100%;height:100%;display:block}.card-name{font-size:12px;line-height:1.35;font-weight:700;padding:10px 9px 4px;min-height:46px}.card-bottom{display:flex;align-items:center;justify-content:space-between;gap:4px;padding:0 9px 10px;font-size:10px;color:#6a795f}.card-stars{font-size:17px;letter-spacing:1px;color:#896620;white-space:nowrap}.completed .card-stars{color:#a47313}.completed .card-top{background:#ecf0e3}.book-footer{display:flex;justify-content:space-between;align-items:center;gap:24px;padding:26px 0 32px}.book-footer p{font-size:12px;line-height:1.7;color:#62745c}.book-footer button{background:#e9ecdf;text-align:left}.book-footer button span{display:block;font-size:11px;font-weight:400;margin-top:4px}.book-button{font-size:12px;white-space:nowrap;background:#e6eddd}.level-bar{flex-wrap:wrap}.level-bar select{flex:1 1 180px}.level-bar .book-button{order:-1}#gallery-title:focus{outline:none}#browse-stars{font-size:12px;width:100%}
@media(min-width:1000px){body:not(.focus-mode) .level-bar .book-button{flex:1 1 100%}}
@media(max-width:1199px){.level-grid{grid-template-columns:repeat(6,minmax(0,1fr))}}
@media(max-width:999px){.level-grid{grid-template-columns:repeat(4,minmax(0,1fr))}}
@media(max-width:760px){.in-book main{width:calc(100% - 28px)!important}.in-book .intro{margin-bottom:22px}.book-heading{gap:12px;align-items:flex-start}.book-heading h2{font-size:30px}.book-heading .eyebrow{font-size:8px;line-height:1.6;letter-spacing:1.1px;max-width:210px}.book-heading p:not(.eyebrow){font-size:12px;max-width:230px}.book-total>strong{font-size:30px}.book-total strong span{font-size:19px}.book-total>span{font-size:7px;letter-spacing:.6px}.book-total p{font-size:10px!important}.level-grid{grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}.book-toolbar{gap:16px}#resume-level{width:100%}#level-filters{gap:6px}#level-filters button{font-size:11px;padding:8px 12px}.book-legend{gap:10px 16px;line-height:1.6}.book-legend span:last-child{flex-basis:100%}.book-footer{align-items:flex-start;flex-direction:column;gap:8px}.book-footer p{margin:0}.book-footer button{width:100%;margin-top:8px}.level-bar select{order:2;flex-basis:100%}.level-bar .progress{margin-left:auto}.level-bar .focus-button{order:1}.book-heading{margin-bottom:18px}}
@media(max-width:520px){.level-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.level-preview{height:166px}.card-name{font-size:13px;min-height:48px}.card-top{padding:9px 11px}.card-number{font-size:23px}.card-difficulty{font-size:8px}.card-bottom{padding:0 10px 11px}.book-heading h2{font-size:27px}}
@media(prefers-reduced-motion:reduce){.level-card{transition:none}.level-card:hover:not(:disabled){transform:none}}
/* Activity 1018: previews stay readable while sequential play is locked. */
.level-card.locked{cursor:default;box-shadow:none}.level-card.locked:hover{transform:none;box-shadow:none;background:#fffdf6}.card-access{display:block;padding:0 9px 9px;color:#65725e;font-size:10px;line-height:1.4;min-height:33px}.locked .card-access{color:#795c32}.card-bottom>span:last-child{display:inline-flex;align-items:center;gap:4px}.lock-icon{width:10px;height:13px;flex-shrink:0}.level-card.next-up{border-color:#42694a;box-shadow:0 3px 0 #91a783}.next-up .card-access{color:#285a3e;font-weight:750}.locked .card-top{background:#eeeee5}.locked[aria-current=true]{outline:none}