:root{color-scheme:light;--paper:#f8f5ef;--white:#fffefa;--ink:#263b39;--muted:#66736e;--orange:#b84e1a;--orange-dark:#933b11;--line:#dcded5;--soft:#eeeee6;font-family:-apple-system,BlinkMacSystemFont,"PingFang SC","Microsoft YaHei",sans-serif;color:var(--ink);background:var(--paper)}*{box-sizing:border-box}body{margin:0;min-width:320px;-webkit-font-smoothing:antialiased}button,textarea{font:inherit}button{cursor:pointer;touch-action:manipulation}button:disabled{cursor:default;opacity:.45}[hidden]{display:none!important}button:focus-visible,a:focus-visible,textarea:focus-visible,summary:focus-visible{outline:3px solid var(--orange);outline-offset:3px}::selection{background:#f0cead;color:var(--ink)}svg{width:19px;height:19px;fill:none;stroke:currentColor;stroke-width:1.7;stroke-linecap:round;stroke-linejoin:round;flex:none}header{max-width:1080px;margin:auto;padding:12px 28px;display:flex;justify-content:space-between;align-items:center;border-bottom:1px solid var(--line)}.back-link{min-height:44px;display:inline-flex;align-items:center;gap:8px;color:var(--ink);font-size:14px;text-decoration:none}.back-link:hover{text-decoration:underline;text-underline-offset:4px}header>span{font-size:12px;color:var(--muted)}main{max-width:860px;margin:auto;padding:28px 28px 32px}.intro{margin-bottom:20px}h1{font-size:32px;line-height:1.3;letter-spacing:-.025em;font-weight:650;margin:0 0 10px}.intro p{font-size:14px;color:var(--muted);line-height:1.8;margin:0}.topics{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:18px}.topics button{min-height:44px;padding:10px 17px;border:1px solid #cbd1c5;border-radius:8px;background:transparent;color:var(--ink);font-size:14px}.topics button[aria-pressed=true]{background:var(--ink);border-color:var(--ink);color:white}.topics button:hover:not(:disabled):not([aria-pressed=true]){background:var(--soft)}.chat{border:1px solid var(--line);border-radius:18px;background:var(--white);overflow:hidden}.chat-head{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:10px 20px;border-bottom:1px solid var(--line)}.chat-head h2{font-size:14px;font-weight:600;line-height:1.6;margin:0}.chat-head button{min-height:44px;padding:9px 0 9px 12px;border:0;background:transparent;color:var(--muted);font-size:12px;flex:none}.messages{height:clamp(260px,43dvh,460px);overflow-y:auto;overscroll-behavior:contain;padding:22px 20px;scrollbar-width:thin;scrollbar-color:#b7c0b7 transparent}.messages::-webkit-scrollbar{width:6px}.messages::-webkit-scrollbar-thumb{background:#b7c0b7;border-radius:6px}.welcome{display:flex;flex-direction:column;align-items:center;justify-content:center;min-height:100%;text-align:center;padding:20px}.welcome h3{font-size:23px;font-weight:500;margin:0 0 10px}.welcome p{max-width:24em;font-size:14px;line-height:1.9;color:var(--muted);margin:0}.message{max-width:90%;width:fit-content;min-width:80px;margin:0 0 18px}.message:last-child{margin-bottom:0}.message.user{margin-left:auto}.speaker{display:block;font-size:11px;color:var(--muted);margin-bottom:7px}.user .speaker{text-align:right}.message-body{white-space:pre-wrap;overflow-wrap:anywhere;font-size:15px;line-height:1.9;background:#f1f2e9;border:1px solid #e1e5d8;border-radius:3px 12px 12px 12px;padding:13px 16px}.user .message-body{background:#f8eadc;border-color:#ead2bb;border-radius:12px 3px 12px 12px}.pending .message-body{color:var(--muted);font-size:13px}.composer-wrap{border-top:1px solid var(--line);padding:12px 16px 16px}.discussion-actions{display:flex;gap:9px;margin-bottom:10px;flex-wrap:wrap}.discussion-actions button{min-height:44px;font-size:12px;color:var(--muted);padding:7px 11px;border:1px solid var(--line);border-radius:7px;background:transparent}.discussion-actions button:hover:not(:disabled){background:var(--soft)}form{display:flex;gap:9px;align-items:stretch}textarea{flex:1;min-width:0;resize:vertical;min-height:76px;max-height:180px;border:1px solid #bac5b5;border-radius:9px;background:var(--white);padding:11px 12px;font-size:16px;line-height:1.65;color:var(--ink);caret-color:var(--orange)}textarea::placeholder{color:var(--muted);opacity:1}.send,.stop{min-width:78px;min-height:48px;padding:12px;border:0;border-radius:9px;display:flex;align-items:center;justify-content:center;gap:5px;font-size:14px;font-weight:600}.send{background:var(--orange);color:white}.send:hover:not(:disabled){background:var(--orange-dark)}.stop{background:var(--soft);color:var(--ink)}.error{font-size:12px;line-height:1.8;color:#8a321c;margin:10px 0 0}.sources{margin-top:14px;color:var(--muted);font-size:12px;line-height:1.9}.sources summary{cursor:pointer;min-height:44px;display:flex;align-items:center;gap:8px}.sources summary::before{content:'+';font-size:18px}.sources[open] summary::before{content:'−'}.sources ul{margin:4px 0 0;padding-left:20px}.sources a{color:var(--muted);text-underline-offset:4px}.sources li{margin:6px 0}.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip-path:inset(50%);white-space:nowrap}
@media(max-width:600px){header{padding:8px 20px}main{padding:22px 18px 24px}h1{font-size:28px;margin-bottom:8px}.intro{margin-bottom:16px}.intro p{font-size:13px}.topics{gap:7px;margin-bottom:15px}.topics button{font-size:13px;padding:9px 13px}.chat{border-radius:15px}.chat-head{padding:7px 14px;gap:8px}.chat-head h2{font-size:13px}.chat-head button{font-size:11px}.messages{height:clamp(240px,40dvh,380px);padding:18px 13px}.message{max-width:94%}.message-body{font-size:15px;line-height:1.85;padding:12px 13px}.welcome{padding:12px}.welcome h3{font-size:21px}.welcome p{font-size:13px}.composer-wrap{padding:10px 12px 12px}.discussion-actions{gap:7px}.discussion-actions button{font-size:11px}textarea{min-height:76px;padding:10px;font-size:16px}.send,.stop{min-width:61px;padding:10px 8px;font-size:13px}.send svg{width:16px;height:16px}.sources{margin-top:8px}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}}
/* Sandstorm classroom focus and three-stage discussion. */
.topic-scope{font-size:14px;font-weight:600;color:var(--orange);line-height:1.8;margin:0 0 8px}.engineering-note{font-size:14px;line-height:1.9;color:var(--muted);margin:0 0 14px}.phase-tabs{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px;margin:0 0 18px}.phase-tabs button{min-height:46px;padding:11px 8px;background:var(--white);border:1px solid #cbd1c5;border-radius:8px;color:var(--ink);font-size:15px;line-height:1.6}.phase-tabs button[aria-pressed=true]{background:#e7ede1;border-color:#7e9477;font-weight:600}.phase-tabs button:hover:not(:disabled){border-color:var(--ink)}h1{letter-spacing:normal}.topics button:first-child{font-weight:600}@media(max-width:600px){.phase-tabs{gap:8px;margin-bottom:15px}.phase-tabs button{font-size:14px}.topic-scope,.engineering-note{font-size:13px}.messages{height:clamp(240px,37dvh,360px)}}