:root{font-family:ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;color:#24392e;background:#f7f8f2;font-synthesis:none;--green:#245a42;--lime:#d9ed98;--muted:#627064}*{box-sizing:border-box}body{margin:0}button,input,select{font:inherit}button,a,input,select{-webkit-tap-highlight-color:transparent}button{cursor:pointer;border:0;border-radius:12px;padding:13px 20px;font-weight:650;transition:background .15s,transform .15s}button:hover{filter:brightness(.96)}button:active{transform:translateY(1px)}:focus-visible{outline:3px solid #ad6409;outline-offset:4px}header,main,footer{width:min(1060px,calc(100% - 48px));margin:auto}header{height:98px;display:flex;align-items:center;justify-content:space-between;border-bottom:1px solid #dce1d6}.brand{display:flex;align-items:center;gap:12px;text-decoration:none;color:inherit;font-weight:750;font-size:20px}.brand>span{display:grid;place-content:center;background:var(--green);color:white;width:42px;height:42px;border-radius:13px;font-size:29px;display:block;text-align:center}.brand-dot{color:var(--lime)}nav{display:flex;gap:8px}.text-button{background:transparent;color:#405c4b}.nav-active{background:#e7eddf;color:#244d37}main{padding:45px 0 60px;min-height:70vh}h1{font-size:clamp(35px,5vw,58px);line-height:1.09;letter-spacing:-2px;margin:14px 0 22px;font-weight:730}em{font-style:normal;color:#507851}h2{font-size:24px;letter-spacing:-.6px;margin:8px 0 14px}p{line-height:1.65}.eyebrow{font-size:11px;letter-spacing:2px;font-weight:750;color:#527052;margin:0}.intro{font-size:16px;color:#657063}.hero{display:grid;grid-template-columns:1.6fr 1fr;align-items:center;min-height:310px;padding-bottom:38px}.pills{display:flex;gap:23px;font-size:13px;margin-top:22px;color:#425a45}.art{height:270px;position:relative;background:radial-gradient(ellipse,#e6edd5 0,transparent 68%)}.tile{position:absolute;border-radius:18px;padding:24px 30px;box-shadow:0 12px 24px #29453212}.t1{left:15%;top:25px;background:#e5edc4;font-size:38px;font-weight:750;transform:rotate(-10deg)}.t2{right:7%;top:100px;background:#285940;color:#e9f3c6;font-size:49px;font-weight:750;transform:rotate(10deg)}.t3{bottom:18px;left:7%;background:#fff;font-size:13px;transform:rotate(-5deg)}.spark{position:absolute;right:8%;top:10px;font-size:58px;color:#d4a04e}.card{background:#fff;border:1px solid #e1e6da;border-radius:24px;padding:32px;margin-bottom:28px;box-shadow:0 5px 18px #2b442805}.section-heading{display:flex;align-items:center;justify-content:space-between;gap:15px;margin-bottom:24px}.section-heading h2{margin-bottom:0}.chip{font-size:12px;background:#f1f3e9;padding:9px 13px;border-radius:24px;white-space:nowrap}fieldset{border:0;padding:0;margin:0}legend,.level-row label{font-size:14px;font-weight:650;margin-bottom:15px}.mode-options{display:grid;grid-template-columns:repeat(3,1fr);gap:14px}.choice{position:relative;cursor:pointer;border:1px solid #dce2d5;border-radius:14px;padding:19px;display:grid;grid-template-columns:42px 1fr;gap:4px 10px;align-items:center}.choice input{position:absolute;right:12px;top:12px;accent-color:var(--green)}.choice strong{font-size:15px}.choice small{grid-column:2;color:#64705e;font-size:12px}.choice.selected{border:2px solid #4f7450;background:#f4f7e9;padding:18px}.symbol{grid-row:span 2;font-size:30px;background:#edf1e3;border-radius:10px;text-align:center}.level-row{display:grid;grid-template-columns:1.3fr 1fr;gap:30px;align-items:end;margin-top:28px}select{display:block;width:100%;padding:14px;border:1px solid #cdd6c7;border-radius:10px;background:white;color:inherit;margin-top:12px}.sample{margin:0;padding:12px 20px;border-left:2px solid #e4eadc}.sample span{display:block;font-size:12px;color:var(--muted)}.sample strong{font-size:20px;font-weight:600}.start-row{display:flex;justify-content:space-between;align-items:center;margin-top:25px;padding-top:20px;border-top:1px solid #e9ecdf;font-size:13px}.primary{background:var(--green);color:white;padding:16px 24px}.primary span{margin-left:40px}.secondary{background:#edf1e7;color:#254b36}.muted{color:var(--muted);font-size:14px}.journey{display:flex;align-items:center;justify-content:space-between;gap:20px;padding:15px 5px}.journey h2{font-size:21px}.badge{display:inline-block;background:#edf2dc;color:#46603d;padding:10px 15px;border-radius:30px;margin:5px;font-size:13px}.badges{margin:20px 0}footer{border-top:1px solid #dce1d6;padding:25px 0 35px;display:flex;justify-content:space-between;font-size:12px;color:#63715f}.stats{display:grid;grid-template-columns:repeat(auto-fit,minmax(130px,1fr));gap:16px;margin:30px 0}.stats>div{padding:23px;background:#edf2e3;border-radius:16px}.stats strong{display:block;font-size:32px;color:var(--green);letter-spacing:-1px}.stats span{display:block;font-size:13px;margin-top:6px}.details{display:flex;flex-wrap:wrap;gap:25px;font-size:14px}.details b{display:block;font-size:18px;margin-top:7px}.callout{background:#f6f5e9;border-left:3px solid #c9b475;padding:20px;border-radius:0 12px 12px 0;margin:28px 0;font-size:14px;line-height:1.7}.actions{display:flex;gap:12px;flex-wrap:wrap;margin-top:25px}.review{list-style:none;padding:0}.review li{display:flex;justify-content:space-between;gap:20px;border-bottom:1px solid #e2e7dc;padding:15px 0}.review span{color:var(--muted)}.practice{max-width:760px;margin:0 auto}.practice-meta,.question-status,.practice-footer{display:flex;justify-content:space-between;align-items:center;gap:15px;font-size:14px}.question-status{margin-top:25px}progress{width:100%;height:8px;accent-color:var(--green);margin-top:15px}.equation{font-size:clamp(44px,7vw,76px);text-align:center;font-weight:750;letter-spacing:-2px;margin:45px 0 30px}.equation span{color:#839078}#answer-form{text-align:center}#answer-form label{display:block;font-size:14px}#answer{display:block;width:min(260px,100%);margin:12px auto;border:2px solid #96ad84;border-radius:14px;padding:15px;font-size:34px;text-align:center;color:var(--green)}#validation{color:#9b3e25;font-size:14px;min-height:24px}.practice-footer{border-top:1px solid #e5eadf;margin-top:32px;padding-top:23px;color:#52634c}.feedback{text-align:center;padding:24px;border-radius:15px;background:#edf4df}.incorrect{background:#faf0dd}.feedback p{margin:5px}.practice .actions{justify-content:center}.centered{text-align:center;padding:65px 25px}.centered button{margin:10px}.filters{display:flex;gap:20px}.filters label{flex:1;font-size:14px}.table-wrap{overflow-x:auto}table{width:100%;border-collapse:collapse;font-size:14px}caption{text-align:left;font-weight:650;padding:15px 0}th,td{text-align:left;padding:16px 12px;border-bottom:1px solid #e4e9dc}th{font-size:12px;color:#64715d}.accuracy-bar{display:block;background:linear-gradient(to right,#e5edce var(--accuracy),transparent var(--accuracy));padding:5px}.empty{text-align:center;padding:45px 15px}.empty>span{font-size:44px;color:#648353}.reset-row{display:flex;justify-content:space-between;gap:15px;font-size:13px}.notice{padding:18px;background:#fff0d3;border:1px solid #d6b16d;border-radius:12px;margin-bottom:20px;font-size:14px}.notice button{margin:8px}a,button,select,input{touch-action:manipulation}@media(max-width:700px){header,main,footer{width:calc(100% - 30px)}header{height:85px}.brand{font-size:17px;gap:7px}nav button{padding:10px;font-size:12px}.hero{grid-template-columns:1fr}.art{display:none}h1{letter-spacing:-1px}.card{padding:22px 18px}.mode-options{grid-template-columns:1fr}.choice{padding:16px}.choice.selected{padding:15px}.level-row{grid-template-columns:1fr;gap:15px}.sample{border-left:0;padding:5px 0}.journey{display:block}.start-row{gap:15px}.primary span{margin-left:12px}.stats{grid-template-columns:repeat(2,1fr)}.stats>div{padding:16px}.stats strong{font-size:27px}.filters{flex-direction:column;gap:10px}.details{gap:20px}.review li{flex-direction:column;gap:5px}.practice-meta{font-size:12px}.practice-footer{font-size:12px}.section-heading{align-items:start}.section-heading h2{font-size:21px}footer{gap:20px}.reset-row{flex-direction:column}.pills{gap:15px;font-size:12px}}@media(prefers-reduced-motion:reduce){*,*::before,*::after{transition:none!important;animation:none!important;scroll-behavior:auto!important}}

/* Stacked arithmetic: shared right edge aligns place values. */
.equation{display:grid;grid-template-columns:auto auto;column-gap:26px;width:max-content;max-width:100%;margin:28px auto 20px;padding:0 10px 10px;border-bottom:3px solid #405c4b;line-height:1.15;font-variant-numeric:tabular-nums;letter-spacing:0}
.equation .operand{color:#24392e;text-align:right}
.equation .top{grid-column:2;grid-row:1}
.equation .operator{grid-column:1;grid-row:2;color:#627064;align-self:center}
.equation .bottom{grid-column:2;grid-row:2}

.answer-response{font-variant-numeric:tabular-nums;font-size:clamp(30px,5vw,44px);font-weight:800;margin:0 0 8px!important}
.answer-correct{color:#19743b}
.answer-incorrect{color:#b42318}
.feedback.correct{background:#e8f4e8}
.feedback.incorrect{background:#fff0ed}
.feedback.correct h2{color:#19743b}
.feedback.incorrect h2,.feedback .hint{color:#a51e16}
.feedback .hint{font-size:18px;font-weight:650;margin-top:12px}
.feedback .answer-note{font-size:14px;color:#69413a}
.auto-advance{position:relative;isolation:isolate;overflow:hidden}
.auto-advance::before{content:"";position:absolute;inset:0 auto 0 0;width:100%;background:#ffffff48;z-index:-1;transform:scaleX(0);transform-origin:left;animation:advance-fill var(--advance-delay,1s) linear forwards}
@keyframes advance-fill{to{transform:scaleX(1)}}
@media(prefers-reduced-motion:reduce){.auto-advance::before{animation:none;transform:scaleX(1)}}