.structure-lab-shell{--sl-blue:#0b7181;--sl-dark:#123f52;--sl-pale:#ecf7f8;--sl-warm:#f7eee7;background:#f7faf9;min-height:calc(100vh - 76px);padding-bottom:35px}.structure-lab-head{background:linear-gradient(118deg,#123f52,#176c7e);color:#fff;padding:32px 0 38px}.structure-lab-back{color:#d7f0f4;text-decoration:none;font-weight:700;font-size:.9rem}.structure-lab-back:hover{color:#fff}.structure-lab-title-row{display:flex;justify-content:space-between;gap:40px;align-items:end;margin-top:18px}.structure-lab-head .eyebrow{color:#ffc89e}.structure-lab-head h1{margin:4px 0 9px;font-size:clamp(2.2rem,5vw,4.2rem);line-height:1.02;letter-spacing:-.045em}.structure-lab-head p{margin:0;max-width:720px;color:#dceef2;font-size:1.06rem}.structure-board-switch{display:flex;background:rgba(255,255,255,.1);padding:5px;border:1px solid rgba(255,255,255,.28);border-radius:12px;flex:0 0 auto}.structure-board-switch button{border:0;background:transparent;color:#e9f7f9;font-weight:800;padding:9px 14px;border-radius:8px}.structure-board-switch button.is-active{background:#fff;color:var(--sl-dark)}.structure-lab-body{margin-top:-1px}.structure-mode-tabs{display:grid;grid-template-columns:repeat(4,1fr);background:#fff;border:1px solid var(--line);border-top:0;border-radius:0 0 15px 15px;overflow:hidden;box-shadow:0 8px 22px rgba(13,58,76,.06)}.structure-mode-tabs button{border:0;border-right:1px solid var(--line);background:#fff;padding:15px 12px;font-weight:800;color:#49606b}.structure-mode-tabs button:last-child{border-right:0}.structure-mode-tabs button span{display:block;font-size:.68rem;letter-spacing:.12em;color:#8a989e}.structure-mode-tabs button.is-active{background:#e8f6f8;color:var(--sl-dark);box-shadow:inset 0 -3px 0 var(--cyan)}.structure-session-bar{display:flex;align-items:center;gap:0;margin:26px 0 14px;border-bottom:1px solid var(--line)}.structure-session-bar>div{display:grid;min-width:105px;padding:0 18px 12px;border-right:1px solid var(--line)}.structure-session-bar>div:first-child{padding-left:0}.structure-session-bar small{font-size:.72rem;text-transform:uppercase;letter-spacing:.08em;color:#74838a;font-weight:800}.structure-session-bar strong{color:var(--navy);font-size:1.08rem}.structure-session-bar button{margin-left:auto;margin-bottom:11px;background:transparent;border:1px solid #91a7ad;border-radius:9px;padding:8px 12px;color:var(--navy);font-weight:750}.structure-workspace{background:#fff;border:1px solid var(--line);border-radius:18px;padding:clamp(22px,4vw,42px);box-shadow:var(--shadow-soft);min-height:420px}.sl-kicker{text-transform:uppercase;letter-spacing:.1em;font-weight:800;color:var(--teal2);font-size:.76rem;margin:0 0 8px}.sl-question-title{font-size:clamp(1.65rem,3vw,2.5rem);line-height:1.13;color:var(--navy);margin:0 0 8px}.sl-question-copy{color:var(--muted);margin:0 0 26px;max-width:800px}.sl-substance{display:flex;align-items:center;gap:20px;padding:22px 0 28px}.sl-formula{display:grid;place-items:center;min-width:116px;min-height:90px;background:var(--sl-pale);border:1px solid #b8d8de;border-radius:16px;font-size:2rem;font-weight:800;color:var(--sl-dark)}.sl-substance div:last-child{display:grid}.sl-substance strong{font-size:1.4rem;color:var(--navy)}.sl-substance small{color:var(--muted)}.sl-options{display:grid;grid-template-columns:repeat(2,1fr);gap:12px}.sl-option{border:1px solid #aebfc4;background:#fff;border-radius:12px;padding:16px;text-align:left;color:var(--navy);font-weight:750;min-height:64px}.sl-option:hover{background:#eef8f9;border-color:#78aab4}.sl-option.is-selected{border:2px solid var(--teal);background:#eaf7f6}.sl-submit{margin-top:22px;border:0;border-radius:11px;padding:12px 19px;background:var(--teal);color:#fff;font-weight:800}.sl-submit:disabled{opacity:.42;cursor:not-allowed}.structure-feedback,.structure-explanation{margin-top:14px;border-radius:14px;padding:18px 20px}.structure-feedback.is-good{background:#ecf8ef;border:1px solid #b9dfc1;color:#155b36}.structure-feedback.is-bad{background:#fff2f0;border:1px solid #efc8c1;color:#832f2f}.structure-feedback strong{display:block;font-size:1.05rem}.structure-explanation{background:#f2f6f5;border:1px solid #d5dfdd;color:var(--ink)}.structure-explanation h2{margin:0 0 10px;color:var(--navy);font-size:1.2rem}.sl-chain{display:grid;grid-template-columns:repeat(4,1fr);gap:8px;margin-top:18px}.sl-chain article{position:relative;background:#fff;border:1px solid #ccd9dc;border-radius:12px;padding:14px;min-height:108px}.sl-chain article:not(:last-child):after{content:'→';position:absolute;right:-13px;top:38%;z-index:2;width:18px;height:24px;background:#f2f6f5;color:var(--teal);font-weight:900;text-align:center}.sl-chain small{display:block;text-transform:uppercase;letter-spacing:.07em;color:#77878e;font-weight:800;font-size:.68rem;margin-bottom:4px}.sl-chain strong{font-size:.91rem;color:var(--navy)}.sl-property-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin:20px 0}.sl-property-card{border:1px solid #cad7da;border-radius:13px;padding:16px;background:#fafcfc}.sl-property-card small{display:block;color:#718087;font-weight:800;text-transform:uppercase;letter-spacing:.06em;font-size:.68rem}.sl-property-card strong{display:block;color:var(--navy);margin:4px 0 10px}.sl-property-card .sl-options{grid-template-columns:1fr}.sl-evidence{list-style:none;padding:0;margin:24px 0;display:grid;border-top:1px solid var(--line)}.sl-evidence li{padding:14px 4px;border-bottom:1px solid var(--line);display:flex;gap:11px}.sl-evidence li:before{content:'•';color:var(--cyan);font-weight:900}.sl-explain-builder{display:grid;gap:14px;margin-top:25px}.sl-explain-builder label{display:grid;gap:6px;color:var(--navy);font-weight:800}.sl-explain-builder select{width:100%;padding:11px 12px;border:1px solid #aab9bd;border-radius:9px;background:#fff;color:var(--ink)}.sl-built-answer{margin-top:20px;background:#f7eee7;border-left:4px solid var(--copper);padding:17px 19px;border-radius:0 12px 12px 0}.sl-built-answer strong{display:block;color:var(--navy);margin-bottom:5px}.sl-board-note{margin-top:20px;font-size:.9rem;color:var(--muted);border-top:1px solid var(--line);padding-top:16px}.structure-lab-foot{display:flex;justify-content:space-between;gap:20px;color:#73828a;font-size:.78rem;padding:16px 2px}.structure-lab-foot a{color:var(--teal2)}@media(max-width:760px){.structure-lab-title-row{display:grid;gap:20px}.structure-board-switch{justify-self:start}.structure-mode-tabs{grid-template-columns:repeat(2,1fr)}.structure-mode-tabs button:nth-child(2){border-right:0}.structure-mode-tabs button:nth-child(-n+2){border-bottom:1px solid var(--line)}.structure-session-bar>div{min-width:0;flex:1;padding-left:10px;padding-right:10px}.structure-session-bar button{font-size:.82rem;padding:7px 8px}.sl-options,.sl-property-grid{grid-template-columns:1fr}.sl-chain{grid-template-columns:1fr}.sl-chain article:not(:last-child):after{content:'↓';right:auto;left:48%;top:auto;bottom:-18px;background:#f2f6f5}.sl-substance{align-items:flex-start}.structure-lab-foot{display:grid}}@media(max-width:430px){.structure-lab-head{padding-top:24px}.structure-session-bar{flex-wrap:wrap}.structure-session-bar button{width:100%;margin:10px 0}.sl-substance{display:grid}.sl-formula{min-width:0;width:100%}}