.tales-page{--tales-blue:#0867df;--tales-ink:#0c1b3a;--tales-muted:#53637e;--tales-rule:#d8e4f2;--tales-orange:#f59c20;--tales-green:#079b8b}
.tales-page .lesson-anchor-card{position:sticky;top:86px;max-height:calc(100vh - 104px);overflow:auto;scrollbar-width:thin}
.tales-page .studio-main{min-width:0}
.tales-section{scroll-margin-top:110px;padding:0 4px 38px;margin:0 0 38px;border-bottom:1px solid var(--tales-rule)}
.tales-section>h2{margin:0 0 16px;color:var(--tales-blue);font-family:Inter,sans-serif;font-size:clamp(1.45rem,2.1vw,2rem);font-weight:700;letter-spacing:-.025em}
.tales-section h3{margin:25px 0 9px;color:var(--tales-ink);font-size:1.08rem;font-weight:700}
.tales-section h4{margin:23px 0 7px;color:var(--tales-ink);font-size:1rem;font-weight:700}
.tales-section p,.tales-section li{color:#364764;line-height:1.68}
.tales-section .lead{font-size:1.05rem;color:#233654}
.tales-definition{margin:20px 0;padding:18px 0;border-top:2px solid var(--tales-blue);border-bottom:1px solid var(--tales-rule)}
.tales-definition strong{display:block;margin-bottom:7px;color:var(--tales-ink);font-size:1.04rem}
.tales-reading{display:grid;grid-template-columns:minmax(150px,220px) 1fr;gap:18px;padding:13px 0;border-bottom:1px solid var(--tales-rule)}
.tales-reading strong{color:var(--tales-ink)}
.tales-reading span{color:#425370;line-height:1.55}
.tales-steps{margin:18px 0;padding:0;list-style:none;counter-reset:tales-step}
.tales-steps li{counter-increment:tales-step;display:grid;grid-template-columns:32px 1fr;gap:12px;padding:12px 0;border-bottom:1px solid var(--tales-rule)}
.tales-steps li::before{content:counter(tales-step);display:grid;place-items:center;width:27px;height:27px;border:1px solid #9fc7f6;border-radius:50%;color:var(--tales-blue);font-weight:700}
.tales-formula{margin:20px 0;padding:16px 0;border-top:1px solid var(--tales-rule);border-bottom:1px solid var(--tales-rule);color:var(--tales-ink);font-family:var(--lesson-math-font);font-size:clamp(1.05rem,2vw,1.3rem);font-weight:600;text-align:center;word-spacing:.15em}
.math-frac{display:inline-grid;grid-template-rows:auto auto;align-items:center;justify-items:stretch;min-width:2em;margin:0 .16em;vertical-align:middle;line-height:1.05;white-space:nowrap}.math-frac>span{display:block;padding-left:.24em;padding-right:.24em;text-align:center}.math-frac>span:first-child{padding-bottom:.13em;border-bottom:1.6px solid currentColor}.math-frac>span:last-child{padding-top:.13em}.tales-section p .math-frac{font-family:var(--lesson-math-font);font-weight:600}
.tales-note{margin:17px 0;padding:13px 15px;background:#f3f7fc;color:#344763;line-height:1.6}
.tales-note strong{color:var(--tales-ink)}
.tales-figure{margin:25px 0 12px}
.tales-figure svg{display:block;width:100%;height:auto;max-height:430px;overflow:visible}
.tales-figure figcaption{margin-top:10px;color:#64748b;font-size:.88rem;line-height:1.55}
.tales-figure .base{fill:none;stroke:#0a66d8;stroke-width:3;stroke-linecap:round;stroke-linejoin:round}
.tales-figure .parallel{fill:none;stroke:#0a66d8;stroke-width:2.6;stroke-linecap:round}
.tales-figure .aux{fill:none;stroke:#079b8b;stroke-width:2.5;stroke-linecap:round}
.tales-figure .extend{fill:none;stroke:#73839b;stroke-width:2;stroke-dasharray:7 7;stroke-linecap:round}
.tales-figure .angle{fill:none;stroke:#f59c20;stroke-width:3;stroke-linecap:round}
.tales-figure .mark{fill:none;stroke:#17284a;stroke-width:2}
.tales-figure .point{fill:#f6a228;stroke:#0c1b3a;stroke-width:1.8}
.tales-figure text{fill:#0c1b3a;font-family:Inter,sans-serif;font-size:18px;font-weight:600}
.tales-figure .small{font-size:15px;font-weight:500}
.tales-two{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:28px;margin:20px 0}
.tales-two>div{min-width:0}
.tales-two h3{margin-top:0}
.tales-table{width:100%;border-collapse:collapse;margin:16px 0}
.tales-table th,.tales-table td{padding:12px 10px;border-bottom:1px solid var(--tales-rule);text-align:left;vertical-align:top}
.tales-table th{color:var(--tales-ink);font-weight:700}
.tales-section .exercise-item{padding:23px 0;border-bottom:1px solid var(--tales-rule)}
.tales-section .exercise-item>strong{display:block;margin-bottom:12px;color:var(--tales-ink);line-height:1.5}
.tales-section .exercise-options{display:grid;gap:8px}
.tales-section .exercise-options>span{display:block;padding:11px 13px;border:1px solid #d2e1f1;border-radius:7px;background:#f8fbff;color:#273a59;cursor:pointer;transition:border-color .16s,background .16s,transform .16s}
.tales-section .exercise-options>span:hover,.tales-section .exercise-options>span:focus{border-color:#78adee;background:#eef6ff;outline:none}
.tales-section .exercise-options>span.is-selected{border-color:var(--tales-blue);background:#e8f2ff;transform:translateX(2px)}
.tales-section .question-check-row{margin-top:12px}
.tales-quiz .exercise-grid{display:block}
.tales-quiz .question-group-title{margin:32px 0 0;padding:13px 0 10px;border-bottom:2px solid var(--tales-blue);color:var(--tales-ink);font-size:1.08rem;font-weight:650}
.tales-quiz .exercise-item{margin:0;padding:23px 2px;border:0;border-bottom:1px solid var(--tales-rule);border-radius:0;background:transparent;box-shadow:none}
.tales-quiz .exercise-item h3{margin:9px 0 13px;font-size:1rem;font-weight:600;line-height:1.58}
.tales-quiz .difficulty-badge{font-size:.72rem;font-weight:600}
.tales-quiz .vf-statements{margin:10px 0 16px;padding-left:2rem}
.tales-quiz .vf-statements li{margin:7px 0;line-height:1.55}
.tales-quiz .exercise-options{grid-template-columns:1fr;gap:7px;margin-top:12px}
.tales-quiz .exercise-options>span{padding:10px 12px;font-weight:400;line-height:1.5}
.tales-quiz .exercise-options>span :is(.math-fraction,.math-frac){display:inline-grid!important;grid-template-rows:auto auto!important;min-width:1.45em!important;margin:0 .12em!important;padding:0!important;border:0!important;border-radius:0!important;background:transparent!important;color:inherit!important;box-shadow:none!important;transform:none!important;vertical-align:middle!important;line-height:1!important;overflow:visible!important}
.tales-quiz .exercise-options>span :is(.math-fraction,.math-frac)>span{display:block!important;min-width:0!important;margin:0!important;padding:.09em .13em 0!important;border:0!important;border-radius:0!important;background:transparent!important;color:inherit!important;box-shadow:none!important;transform:none!important;text-align:center!important;font-weight:inherit!important;line-height:1!important;overflow-wrap:normal!important;cursor:inherit!important;transition:none!important}
.tales-quiz .exercise-options>span :is(.math-fraction,.math-frac)>span:first-child{padding:.02em .13em .09em!important;border-bottom:1.5px solid currentColor!important}
.tales-quiz .exercise-options>span.is-selected{color:#075fc9;border-color:#77afea;background:#eaf4ff;box-shadow:inset 4px 0 0 var(--tales-blue);font-weight:600;transform:none}
.tales-quiz .exercise-options>span.is-correct{color:#075f46;border-color:#7ed8b8;background:#e9fbf4;box-shadow:inset 4px 0 0 #15966f}
.tales-quiz .exercise-options>span.is-wrong{color:#8f1f1f;border-color:#f5a3a3;background:#fff0f0;box-shadow:inset 4px 0 0 #d84141}
.tales-quiz .question-check-row{display:flex;align-items:center;gap:12px;margin-top:14px}
.tales-quiz .question-check-button{min-width:150px;padding:8px 14px;font-size:.86rem;font-weight:600}
.tales-quiz .question-check-result{font-size:.9rem;font-weight:600}
.tales-quiz .exercise-item.is-correct .question-check-result{color:#08765a}
.tales-quiz .exercise-item.is-wrong .question-check-result{color:#a12b2b}
.tales-quiz .answer-explanation{display:none;margin:14px 0 0;padding:11px 0 0;border-top:1px dashed var(--tales-rule);font-size:.94rem;line-height:1.58}
.tales-quiz .exercise-item.is-question-checked .answer-explanation{display:block}
.tales-quiz .question-sketch{display:flex;justify-content:center;gap:42px;margin:15px 0;padding:14px 0;border-top:1px solid var(--tales-rule);border-bottom:1px solid var(--tales-rule);color:var(--tales-ink);font-family:var(--lesson-math-font);font-size:1.04rem;font-weight:600}
html[data-theme="dark"] .tales-quiz .exercise-options>span.is-selected{color:#b9d9ff;background:#17345a}
html[data-theme="dark"] .tales-quiz .exercise-options>span.is-correct{color:#bdf4df;background:#123c33;border-color:#3d9478}
html[data-theme="dark"] .tales-quiz .exercise-options>span.is-wrong{color:#ffd0d0;background:#482326;border-color:#a95a61}
.tales-page .studio-bottom-nav--next-only{display:flex;justify-content:flex-end}
.tales-quiz .exercise-grid{display:block}
.tales-quiz .question-group-title{margin:32px 0 0;padding:13px 0 10px;border-bottom:2px solid var(--tales-blue);color:var(--tales-ink);font-size:1.08rem;font-weight:650}
.tales-quiz .exercise-item{margin:0;padding:23px 2px;border:0;border-bottom:1px solid var(--tales-rule);border-radius:0;background:transparent;box-shadow:none}
.tales-quiz .exercise-item h3{margin:9px 0 13px;font-size:1rem;font-weight:600;line-height:1.58}
.tales-quiz .difficulty-badge{font-size:.72rem;font-weight:600}
.tales-quiz .vf-statements{margin:10px 0 16px;padding-left:2rem}
.tales-quiz .vf-statements li{margin:7px 0;line-height:1.55}
.tales-quiz .exercise-options{grid-template-columns:1fr;gap:7px;margin-top:12px}
.tales-quiz .exercise-options>span{padding:10px 12px;font-weight:400;line-height:1.5}

.tales-quiz .exercise-options>span.is-selected{color:#075fc9;border-color:#77afea;background:#eaf4ff;box-shadow:inset 4px 0 0 var(--tales-blue);font-weight:600;transform:none}
.tales-quiz .exercise-options>span.is-correct{color:#075f46;border-color:#7ed8b8;background:#e9fbf4;box-shadow:inset 4px 0 0 #15966f}
.tales-quiz .exercise-options>span.is-wrong{color:#8f1f1f;border-color:#f5a3a3;background:#fff0f0;box-shadow:inset 4px 0 0 #d84141}
.tales-quiz .question-check-row{display:flex;align-items:center;gap:12px;margin-top:14px}
.tales-quiz .question-check-button{min-width:150px;padding:8px 14px;font-size:.86rem;font-weight:600}
.tales-quiz .question-check-result{font-size:.9rem;font-weight:600}
.tales-quiz .exercise-item.is-correct .question-check-result{color:#08765a}
.tales-quiz .exercise-item.is-wrong .question-check-result{color:#a12b2b}
.tales-quiz .answer-explanation{display:none;margin:14px 0 0;padding:11px 0 0;border-top:1px dashed var(--tales-rule);font-size:.94rem;line-height:1.58}
.tales-quiz .exercise-item.is-question-checked .answer-explanation{display:block}
.tales-quiz .question-sketch{display:flex;justify-content:center;gap:42px;margin:15px 0;padding:14px 0;border-top:1px solid var(--tales-rule);border-bottom:1px solid var(--tales-rule);color:var(--tales-ink);font-family:var(--lesson-math-font);font-size:1.04rem;font-weight:600}
html[data-theme="dark"] .tales-quiz .exercise-options>span.is-selected{color:#b9d9ff;background:#17345a}
html[data-theme="dark"] .tales-quiz .exercise-options>span.is-correct{color:#bdf4df;background:#123c33;border-color:#3d9478}
html[data-theme="dark"] .tales-quiz .exercise-options>span.is-wrong{color:#ffd0d0;background:#482326;border-color:#a95a61}
.tales-page .studio-bottom-nav--next-only .button{flex:none;width:auto;min-width:132px;padding-inline:20px}
.tales-proof-head{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:0;margin:22px 0;border-top:1px solid var(--tales-rule);border-bottom:1px solid var(--tales-rule)}
.tales-proof-head>div{padding:16px 20px 17px 0}
.tales-proof-head>div+div{padding-left:24px;border-left:1px solid var(--tales-rule)}
.tales-proof-head>div>span,.tales-proof-summary>span{display:block;margin-bottom:6px;color:#5b6d87;font-size:.76rem;font-weight:700;letter-spacing:.075em;text-transform:uppercase}
.tales-proof-head strong{display:block;color:var(--tales-ink);font-family:var(--lesson-math-font);font-size:1.08rem}
.tales-proof-head p{margin:7px 0 0;font-size:.93rem;line-height:1.5}
.tales-proof-figure{margin-top:30px;margin-bottom:28px}
.tales-figure .equal-mark{fill:none;stroke:#17284a;stroke-width:2;stroke-linecap:round}
.tales-figure .proof-bars{fill:none;stroke:#0867df;stroke-width:4;stroke-linecap:round}
.tales-figure .construction{fill:none;stroke:#667a96;stroke-width:2.2;stroke-dasharray:7 6}
.tales-figure .proof-fill{stroke:none;opacity:.16}
.tales-figure .proof-fill-a{fill:#f59c20}
.tales-figure .proof-fill-b{fill:#079b8b}
.tales-figure text.proof-label{fill:#586a84;font-size:14px;font-weight:700;letter-spacing:.05em;text-transform:uppercase}
.tales-figure text.proof-equation{font-family:var(--lesson-math-font);font-size:20px;font-weight:600}
.tales-figure text.proof-conclusion{font-family:"Cambria Math",Cambria,serif;font-size:22px;font-weight:700}
.tales-proof-summary{margin:24px 0;padding:17px 0;border-top:1px solid var(--tales-rule);border-bottom:1px solid var(--tales-rule);text-align:center}
.tales-proof-summary strong{display:block;color:var(--tales-ink);font-family:var(--lesson-math-font);font-size:clamp(1.05rem,2vw,1.25rem)}
html[data-theme="dark"] .tales-page{--tales-ink:#eef5ff;--tales-muted:#b7c5da;--tales-rule:#32435c}
html[data-theme="dark"] .tales-section p,html[data-theme="dark"] .tales-section li,html[data-theme="dark"] .tales-reading span{color:#c6d1e1}
html[data-theme="dark"] .tales-note{background:#17253a;color:#c8d5e8}
html[data-theme="dark"] .tales-figure text{fill:#eef5ff}
html[data-theme="dark"] .tales-section .exercise-options>span{background:#13233a;border-color:#344b68;color:#dce7f7}
@media(max-width:1040px){.tales-page .lesson-anchor-card{position:static;max-height:none;overflow:visible}}
@media(max-width:720px){.tales-proof-head{grid-template-columns:1fr}.tales-proof-head>div+div{padding-left:0;border-left:0;border-top:1px solid var(--tales-rule)}.tales-two{grid-template-columns:1fr;gap:8px}.tales-reading{grid-template-columns:1fr;gap:5px}.tales-figure text{font-size:15px}.tales-figure .small{font-size:13px}}
@media(prefers-reduced-motion:reduce){.tales-section .exercise-options>span{transition:none}}
/* similarity guided example */
.similarity-page .tales-steps li > div{min-width:0}
.similarity-page .tales-steps li > div > strong{display:block;color:var(--tales-ink);margin-bottom:.35rem}
.similarity-page .tales-steps li p{margin:.25rem 0 .55rem;max-width:72ch}
.similarity-page .step-formula{display:flex;align-items:center;flex-wrap:wrap;gap:.4rem;margin:.45rem 0 .1rem;color:var(--tales-ink);font-family:var(--lesson-math-font);font-size:1.15rem;font-weight:600}
.similarity-page .step-correspondence{display:flex;flex-wrap:wrap;gap:.55rem 1.5rem;margin-top:.45rem;color:var(--tales-ink);font-family:var(--lesson-math-font);font-size:1.08rem;font-weight:600}