:root{--bg:#f0f4f8;--surface:#fff;--surface-2:#f8fafc;--surface-3:#f1f5f9;--border:#e2e8f0;--border-mid:#cbd5e1;--border-strong:#94a3b8;--text:#0f172a;--text-mid:#334155;--text-muted:#64748b;--text-subtle:#94a3b8;--accent:#6366f1;--accent-light:#eef2ff;--accent-mid:#818cf8;--accent-dark:#4f46e5;--success:#059669;--success-light:#ecfdf5;--success-border:#a7f3d0;--error:#dc2626;--error-light:#fef2f2;--error-border:#fecaca;--code-bg:#fafafa;--code-border:#e2e8f0;--code-line:#f1f5f9;--pill-prop-bg:#eef2ff;--pill-prop-color:#4338ca;--pill-prop-border:#c7d2fe;--pill-val-bg:#ecfdf5;--pill-val-color:#065f46;--pill-val-border:#a7f3d0;--radius-sm:6px;--radius-md:12px;--radius-lg:16px;--radius-xl:24px;--shadow-xs:0 1px 2px #0f172a0f;--shadow-sm:0 1px 3px #0f172a14, 0 1px 2px #0f172a0a;--shadow-md:0 4px 12px #0f172a14, 0 2px 4px #0f172a0a;--shadow-lg:0 12px 32px #0f172a1a, 0 4px 8px #0f172a0f;--font-code:"Fira Code", "Cascadia Code", "JetBrains Mono", "Consolas", monospace}*,:before,:after{box-sizing:border-box;margin:0;padding:0}html{font-size:16px}body{background:var(--bg);color:var(--text);-webkit-font-smoothing:antialiased;min-height:100vh;font-family:Inter,Segoe UI,system-ui,-apple-system,sans-serif;line-height:1.5}button{cursor:pointer;font:inherit;border:none}.home-page{max-width:680px;margin:0 auto;padding:56px 20px 80px}.home-header{text-align:center;margin-bottom:48px}.home-header__badge{background:var(--accent-light);color:var(--accent-dark);letter-spacing:.08em;text-transform:uppercase;border:1px solid var(--pill-prop-border);border-radius:999px;align-items:center;gap:6px;margin-bottom:20px;padding:5px 14px;font-size:12px;font-weight:700;display:inline-flex}.home-header__title{letter-spacing:-.03em;color:var(--text);margin-bottom:14px;font-size:clamp(2.2rem,5vw,3.2rem);font-weight:800;line-height:1.1}.home-header__title span{background:linear-gradient(135deg, var(--accent) 0%, #8b5cf6 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var(--border);width:38px;height:38px;color:var(--text-muted);border-radius:10px;flex-shrink:0;justify-content:center;align-items:center;font-size:14px;font-weight:700;display:flex}.activity-card--done .activity-card__number{background:var(--success-light);border-color:var(--success-border);color:var(--success)}.activity-card__body{flex:1;min-width:0}.activity-card__row{flex-wrap:wrap;align-items:center;gap:8px;margin-bottom:3px;display:flex}.activity-card__title{color:var(--text);font-size:1rem;font-weight:700}.activity-card__badge{border:1px solid;border-radius:999px;padding:2px 9px;font-size:11px;font-weight:600}.activity-card__done-badge{color:var(--success);background:var(--success-light);border:1px solid var(--success-border);border-radius:999px;padding:2px 9px;font-size:11px;font-weight:600}.activity-card__desc{color:var(--text-muted);white-space:nowrap;text-overflow:ellipsis;font-size:.875rem;overflow:hidden}.activity-card__arrow{color:var(--text-subtle);flex-shrink:0;font-size:1.1rem;transition:transform .15s,color .15s}.activity-card:hover .activity-card__arrow{color:var(--accent);transform:translate(3px)}.activity-page{flex-direction:column;max-width:1120px;min-height:100vh;margin:0 auto;padding:0 20px 48px;display:flex}.activity-header{border-bottom:1px solid var(--border);flex-wrap:wrap;justify-content:space-between;align-items:center;gap:16px;margin-bottom:20px;padding:14px 0;display:flex}.activity-header__centre{flex-direction:column;flex:1;align-items:center;gap:3px;display:flex}.activity-header__title{color:var(--text);letter-spacing:-.01em;font-size:1.2rem;font-weight:700}.activity-header__nav{align-items:center;gap:6px;display:flex}.activity-header__count{color:var(--text-muted);white-space:nowrap;padding:0 4px;font-size:12px}.activity-instructions{background:var(--accent-light);border:1px solid var(--pill-prop-border);border-left:4px solid var(--accent);border-radius:var(--radius-md);margin-bottom:20px;padding:18px 20px}.activity-instructions__header{align-items:center;gap:8px;margin-bottom:8px;display:flex}.activity-instructions__icon{font-size:1.1rem}.activity-instructions__label{letter-spacing:.08em;text-transform:uppercase;color:var(--accent);font-size:.7rem;font-weight:700}.activity-instructions__goal{color:var(--text-primary);margin:0 0 12px;font-size:.95rem;font-weight:600;line-height:1.5}.activity-instructions__steps{counter-reset:steps;flex-direction:column;gap:6px;margin:0;padding:0;list-style:none;display:flex}.activity-instructions__step{counter-increment:steps;color:var(--text-secondary);align-items:flex-start;gap:10px;font-size:.875rem;line-height:1.5;display:flex}.activity-instructions__step:before{content:counter(steps);background:var(--accent);color:#fff;border-radius:50%;flex-shrink:0;justify-content:center;align-items:center;width:20px;height:20px;margin-top:1px;font-size:.7rem;font-weight:700;display:flex}.result-banner{border-radius:var(--radius-md);align-items:center;gap:10px;margin-bottom:16px;padding:13px 18px;font-size:.9rem;animation:.2s slideIn;display:flex}.result-banner--correct{background:var(--success-light);border:1px solid var(--success-border);color:var(--success)}.result-banner--incorrect{background:var(--error-light);border:1px solid var(--error-border);color:var(--error)}@keyframes slideIn{0%{opacity:0;transform:translateY(-6px)}to{opacity:1;transform:translateY(0)}}.activity-content{grid-template-columns:1fr 300px;gap:16px;margin-bottom:16px;display:grid}@media (width<=720px){.activity-content{grid-template-columns:1fr}}.code-display{background:var(--code-bg);border:1px solid var(--code-border);border-radius:var(--radius-md);box-shadow:var(--shadow-sm);overflow:hidden}.code-display__header{background:var(--surface-3);border-bottom:1px solid var(--code-border);align-items:center;gap:6px;padding:10px 16px;display:flex}.code-display__dot{background:var(--border-mid);border-radius:50%;width:11px;height:11px}.code-display__dot:first-child{background:#fc6058}.code-display__dot:nth-child(2){background:#ffa400}.code-display__dot:nth-child(3){background:#00ca56}.code-display__filename{color:var(--text-muted);font-size:12px;font-family:var(--font-code);margin-left:8px}.code-display__body{font-family:var(--font-code);white-space:pre-wrap;word-break:break-word;background:var(--code-bg);padding:24px 28px;font-size:.95rem;line-height:2.1}.syn-selector{color:maroon;font-weight:500}.syn-property{color:#0451a5}.syn-value{color:#098658}.syntax-punct{color:#6e7781}.blank-slot{border:2px dashed var(--border-mid);background:var(--surface);vertical-align:middle;border-radius:999px;justify-content:center;align-items:center;min-height:32px;margin:0 3px;transition:border-color .15s,background .15s,box-shadow .15s,transform .12s;display:inline-flex;position:relative}.blank-slot--empty,.blank-slot--drag-active,.blank-slot--over{min-width:88px}.blank-slot__hint{color:var(--text-subtle);font-size:11px;font-family:var(--font-code);pointer-events:none;white-space:nowrap;padding:0 14px}.blank-slot--drag-active{border-style:solid;border-color:var(--accent);background:var(--accent-light);animation:1.2s ease-in-out infinite pulse-blank}.blank-slot--filled-drag-active{border-style:solid;border-color:var(--accent-mid);background:var(--accent-light);animation:1.2s ease-in-out infinite pulse-blank-soft}@keyframes pulse-blank{0%,to{box-shadow:0 0 #6366f100}50%{border-color:var(--accent-mid);box-shadow:0 0 0 5px #6366f133}}@keyframes pulse-blank-soft{0%,to{box-shadow:0 0 #6366f100}50%{box-shadow:0 0 0 3px #6366f126}}.blank-slot--over{border-style:solid;border-color:var(--accent-dark);background:var(--accent-light);transform:scale(1.05);box-shadow:0 0 0 4px 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.12s;display:inline-flex}.pill:active{cursor:grabbing;transform:scale(.97)}.pill--property{background:var(--pill-prop-bg);color:var(--pill-prop-color);border-color:var(--pill-prop-border)}.pill--property:hover{background:#e0e7ff;box-shadow:0 0 0 3px #6366f133}.pill--value{background:var(--pill-val-bg);color:var(--pill-val-color);border-color:var(--pill-val-border)}.pill--value:hover{background:#d1fae5;box-shadow:0 0 0 3px #10b98133}.pill--overlay{box-shadow:var(--shadow-lg);cursor:grabbing;opacity:.95;transform:rotate(1.5deg)scale(1.06)}.pill--correct{cursor:default;box-shadow:none;background:var(--success-light)!important;color:var(--success)!important;border-color:var(--success-border)!important}.pill--incorrect{background:var(--error-light)!important;color:var(--error)!important;border-color:var(--error-border)!important}.pill--dragging{opacity:.2}.pill--disabled{cursor:default}.pill--legend{cursor:default;pointer-events:none;padding:3px 10px;font-size:.78rem}.pill-tray{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-md);min-height:76px;box-shadow:var(--shadow-xs);margin-bottom:16px;padding:14px 18px;transition:border-color .15s,background .15s}.pill-tray--over{border-color:var(--accent);background:var(--accent-light)}.pill-tray__header{flex-wrap:wrap;justify-content:space-between;align-items:center;gap:8px;margin-bottom:12px;display:flex}.pill-tray__label{letter-spacing:.08em;text-transform:uppercase;color:var(--text-subtle);font-size:11px;font-weight:700}.pill-tray__legend{align-items:center;gap:6px;display:flex}.pill-tray__pills{flex-wrap:wrap;gap:8px;display:flex}.pill-tray__empty{color:var(--text-subtle);font-size:.875rem;font-style:italic}.preview-panel{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-md);box-shadow:var(--shadow-xs);overflow:hidden}.preview-panel__label{letter-spacing:.08em;text-transform:uppercase;color:var(--text-subtle);border-bottom:1px solid var(--border);background:var(--surface-3);padding:10px 16px;font-size:11px;font-weight:700}.preview-panel__stage{background-color:#f8fafc;background-image:linear-gradient(#6366f10a 1px,#0000 1px),linear-gradient(90deg,#6366f10a 1px,#0000 1px);background-position:0 0;background-repeat:repeat;background-size:20px 20px;background-attachment:scroll;background-origin:padding-box;background-clip:border-box;justify-content:center;align-items:center;min-height:160px;padding:32px 24px;display:flex}.preview-target{width:100%;max-width:260px}.btn-primary,.btn-secondary,.btn-success,.btn-ghost{border-radius:var(--radius-sm);justify-content:center;align-items:center;gap:6px;padding:8px 18px;font-size:.875rem;font-weight:600;transition:background .14s,box-shadow .14s,opacity .14s,transform .1s;display:inline-flex}.btn-primary{background:var(--accent);color:#fff}.btn-primary:hover:not(:disabled){background:var(--accent-dark);box-shadow:0 0 0 3px #6366f140}.btn-primary:disabled{opacity:.4;cursor:not-allowed}.btn-success{background:var(--success);color:#fff}.btn-success:hover{background:#047857;box-shadow:0 0 0 3px #05966940}.btn-secondary{background:var(--surface);color:var(--text-mid);border:1px solid var(--border-mid)}.btn-secondary:hover{background:var(--surface-3);border-color:var(--border-strong)}.btn-ghost{color:var(--text-muted);background:0 0;border:1px solid #0000;padding:7px 12px}.btn-ghost:hover:not(:disabled){background:var(--surface-3);color:var(--text);border-color:var(--border)}.btn-ghost:disabled{opacity:.35;cursor:not-allowed}.activity-actions{flex-wrap:wrap;align-items:center;gap:10px;margin-bottom:28px;display:flex}.activity-footer-nav{border-top:1px solid var(--border);justify-content:space-between;padding-top:18px;display:flex}