:root{color-scheme:light;--ink:#253d31;--muted:#526456;--green:#347951;--light:#eaf3e9;--line:#dce6da;--cream:#f6f8f2;--purple:#ede6f7;--red:#b3323e}*{box-sizing:border-box}body{margin:0;background:var(--cream);font-family:var(--font-family);color:var(--ink);font-size:var(--font-body,1rem);line-height:1.7}a{color:var(--green)}button,select{font:inherit;color:inherit}button{cursor:pointer;background:#fff;border:1px solid var(--line);border-radius:8px;padding:9px 13px;line-height:1.5}button:hover{border-color:#82ab83;background:#f0f6ed}button:focus-visible,a:focus-visible,select:focus-visible,input:focus-visible,summary:focus-visible{outline:3px solid #daa536;outline-offset:2px}button:disabled{opacity:.45;cursor:default}button.primary{background:var(--green);color:#fff;border-color:var(--green)}button.primary:hover{background:#276840}button[aria-pressed=true]{background:#d7ead4;border-color:#69a074;color:#235938}select{width:100%;border:1px solid var(--line);background:#fff;border-radius:7px;padding:9px;margin-top:4px;min-height:42px}h1,h2,p{margin:0}h1{font-size:var(--font-page,1.625rem);letter-spacing:normal;line-height:1.4;font-weight:600}h2{font-size:var(--font-section,1.375rem);line-height:1.5;font-weight:600}.topbar{min-height:72px;display:flex;align-items:center;justify-content:space-between;padding:16px max(24px,calc((100vw - 1250px)/2));gap:20px;background:#fff;border-bottom:1px solid var(--line)}.brand{font-size:21px;font-weight:600;text-decoration:none;white-space:nowrap}.topbar nav{display:flex;gap:23px;flex-wrap:wrap;font-size:var(--font-small,.9375rem)}.topbar nav a{text-decoration:none}.topbar nav [aria-current]{font-weight:600;color:#365a40}.variant-shell{max-width:1250px;padding:32px 24px 48px;margin:auto}.page-heading{display:flex;justify-content:space-between;gap:30px;align-items:center;margin-bottom:25px}.page-heading>div>p:last-child{color:var(--muted);margin-top:12px}.eyebrow{font-size:var(--font-small,.9375rem);color:var(--green);letter-spacing:normal;margin-bottom:7px}.overall-progress{background:#e4eee1;border-radius:12px;min-width:145px;text-align:center;padding:14px 20px;flex:none}.overall-progress strong{font-size:25px;display:block;color:var(--green)}.overall-progress span{font-size:var(--font-small,.9375rem);color:var(--muted)}.variant-types{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:12px;margin-bottom:24px}.type-button{text-align:left;display:flex;gap:12px;padding:17px 15px;align-items:center;background:#fff;border-radius:12px}.type-button[aria-pressed=true]{box-shadow:0 0 0 1px #69a074;background:#edf5e8}.type-icon{width:40px;height:42px;flex:none;border-radius:9px;display:grid;place-items:center;background:#edf2e7;font-size:25px;color:var(--green);font-weight:600}.type-button strong{display:block;font-size:16px;line-height:1.4}.type-button small{display:block;font-size:var(--font-body,1rem);color:var(--muted);margin-top:5px}.play-layout{display:grid;grid-template-columns:minmax(0,1fr) 325px;gap:24px;align-items:start}.play-card,.side-card{background:#fff;border:1px solid var(--line);border-radius:13px;padding:24px}.board-heading{display:flex;align-items:center;justify-content:space-between;gap:12px;margin-bottom:18px}.board-heading .eyebrow{font-size:var(--font-small,.9375rem);margin-bottom:3px}.level-badge{border:1px solid #cddfc5;background:#f1f7ec;color:#537748;border-radius:25px;padding:4px 12px;white-space:nowrap;font-size:var(--font-small,.9375rem)}.puzzle-picker{display:flex;gap:12px;margin-bottom:15px;font-size:var(--font-small,.9375rem)}.puzzle-picker label{width:42%;color:var(--muted)}.puzzle-picker .puzzle-choice{flex:1}.rules{font-size:var(--font-small,.9375rem);line-height:1.85;color:#526d59;background:#f2f7ef;padding:11px 14px;border-radius:8px;margin-bottom:20px}.variant-board{display:grid;grid-template-columns:repeat(var(--size),minmax(0,1fr));border:2px solid #3f644b;max-width:540px;margin:0 auto;background:#fff;aspect-ratio:1;width:100%}.variant-cell{position:relative;display:grid;place-items:center;aspect-ratio:1;border:0;border-right:1px solid #d9e3d7;border-bottom:1px solid #d9e3d7;border-radius:0;padding:0;background:#fff;min-width:0;line-height:1;color:#3e79b1;font-size:clamp(21px,3vw,34px);isolation:isolate}.variant-cell.given{color:#2e4936;font-weight:600}.variant-cell.given::after{content:"";position:absolute;inset:0;background:#7b947508;z-index:-1}.variant-cell.box-right{border-right:2px solid #688466}.variant-cell.box-bottom{border-bottom:2px solid #688466}.variant-cell.edge-right{border-right:0}.variant-cell.edge-bottom{border-bottom:0}.variant-cell.diagonal{background:#eaf4e2}.variant-cell.peer{background:#f2f6ef}.variant-cell.diagonal.peer{background:#e2eed9}.variant-cell.knight-peer{background:var(--purple)}.variant-cell.same-value{color:#23663c;background:#e3f1df}.variant-cell.selected{background:#d4e8cf;box-shadow:inset 0 0 0 2px #5a985e;z-index:1}.variant-cell.conflict{color:var(--red);background:#ffe4e2}.variant-cell:hover{background:#e6f0df}.variant-cell:focus{outline:none}.variant-cell:focus-visible{box-shadow:inset 0 0 0 3px #c39328;z-index:2}.variant-board[data-size="4"]{max-width:390px}.variant-board[data-size="4"] .variant-cell{font-size:42px}.variant-board[data-size="6"]{max-width:480px}.variant-board[data-size="6"] .variant-cell{font-size:34px}.cell-notes{display:grid;grid-template-columns:repeat(var(--note-cols),1fr);grid-template-rows:repeat(var(--note-rows),1fr);position:absolute;inset:3px;align-items:center;text-align:center;color:#77916d;font-size:11px;font-weight:450;line-height:1}.variant-board[data-size="4"] .cell-notes{font-size:17px}.variant-board[data-size="6"] .cell-notes{font-size:14px}.selection-status{display:flex;gap:10px;justify-content:space-between;font-size:var(--font-body,1rem);color:var(--muted);max-width:540px;margin:12px auto}.number-pad{display:grid;grid-template-columns:repeat(var(--size),minmax(0,1fr));gap:7px;max-width:540px;margin:0 auto 14px}.number-pad button{font-size:22px;padding:8px 0;color:var(--green);background:#f4f8f0}.play-actions{display:flex;gap:8px;max-width:540px;margin:0 auto;flex-wrap:wrap}.play-actions button{flex:1;white-space:nowrap;min-width:80px;font-size:var(--font-body,1rem)}.feedback{font-size:var(--font-body,1rem);line-height:1.8;color:#5a7955;min-height:47px;margin:15px auto 0;max-width:540px}.feedback.error{color:var(--red)}.progress-track{height:5px;background:#edf2e8;border-radius:5px;overflow:hidden;max-width:540px;margin:auto}.progress-track span{display:block;background:#81b279;height:100%;transition:width .2s}.keyboard-help{font-size:var(--font-small,.9375rem);color:#526456;text-align:center;margin-top:17px}.completion{max-width:540px;margin:18px auto 0;background:#eaf4e3;border:1px solid #b8d2aa;border-radius:10px;padding:17px;text-align:center}.completion strong{color:#337345;font-size:20px}.completion p{font-size:var(--font-body,1rem);color:#526456;margin:5px 0 12px}.completion button{background:#fff}.practice-sidebar{display:grid;gap:16px}.side-card{padding:20px}.side-card h2{font-size:var(--font-section,1.375rem);margin-bottom:10px;font-weight:600}.side-card p{font-size:var(--font-body,1rem);line-height:1.9;color:var(--muted)}.side-card p+p{margin-top:10px}.candidate-option{font-size:var(--font-body,1rem);display:flex;gap:7px;align-items:flex-start;margin-top:17px}.candidate-option input{margin:5px 0 0;accent-color:var(--green)}.candidate-preview{margin-top:10px;padding:10px;background:#eff6e8;border-radius:7px;color:#426e3a;font-size:13px}.side-card .small{font-size:var(--font-small,.9375rem);margin-top:12px;line-height:1.8}.puzzle-map{display:grid;grid-template-columns:repeat(6,minmax(0,1fr));gap:6px;margin:15px 0}.puzzle-map button{padding:7px 0;font-size:var(--font-body,1rem);border-radius:6px}.puzzle-map button.done{background:#e7f1e2;color:#4c8346}.puzzle-map button.current{border:2px solid #5c955e;padding:6px 0;font-weight:600;background:#dcebd4}.puzzle-map button.level-start{border-top-color:#608b56}.journey-actions{display:grid;gap:8px}.journey-actions button{font-size:var(--font-body,1rem)}.side-card summary{cursor:pointer;font-weight:600;font-size:var(--font-body,1rem)}.side-card[open] summary{margin-bottom:12px}.back-link{font-size:var(--font-body,1rem);text-decoration:none;padding:0 6px}dialog{max-width:440px;width:calc(100% - 32px);padding:25px;border:1px solid var(--line);border-radius:14px;color:var(--ink)}dialog::backdrop{background:#1f35284d}dialog h2{font-size:var(--font-section,1.375rem);margin-bottom:10px;font-weight:600}dialog p{font-size:var(--font-body,1rem);line-height:1.9;color:var(--muted)}.dialog-actions{display:flex;justify-content:flex-end;gap:9px;margin-top:21px}[hidden]{display:none!important}@media(min-width:1400px){.play-card{padding:28px 35px}.variant-cell{font-size:36px}}@media(max-width:1000px){.play-layout{grid-template-columns:minmax(0,1fr) 285px;gap:18px}.type-button{padding:13px 10px;gap:8px}.type-button strong{font-size:var(--font-body,1rem)}.type-icon{width:30px;height:35px;font-size:23px}.variant-shell{padding:25px 20px}.play-card{padding:20px}.side-card{padding:17px}}@media(max-width:800px){.play-layout{grid-template-columns:minmax(0,1fr)}.practice-sidebar{grid-template-columns:1fr 1fr;align-items:start}.practice-sidebar details{grid-column:1/-1}.variant-cell{font-size:clamp(23px,5.4vw,35px)}.variant-types{grid-template-columns:repeat(2,minmax(0,1fr))}.type-button strong{font-size:16px}.topbar{padding:14px 20px;gap:12px}.topbar nav{gap:14px;font-size:var(--font-small,.9375rem)}.page-heading{gap:18px}.overall-progress{min-width:112px;padding:12px}.overall-progress strong{font-size:22px}}@media(max-width:520px){.variant-shell{padding:22px 12px 35px}.topbar{padding:13px 14px;flex-wrap:wrap;gap:6px}.brand{font-size:19px}.topbar nav{width:100%;justify-content:space-between;gap:9px;font-size:var(--font-small,.9375rem)}.page-heading{display:block;position:relative;padding-right:0;margin-bottom:20px}.page-heading h1{font-size:var(--font-page,1.625rem);max-width:350px;font-weight:600}.page-heading>div>p:last-child{font-size:var(--font-body,1rem)}.overall-progress{display:inline-flex;align-items:baseline;gap:8px;margin-top:13px;padding:5px 12px;min-width:0}.overall-progress strong{font-size:17px}.overall-progress span{font-size:var(--font-small,.9375rem)}.eyebrow{font-size:var(--font-small,.9375rem)}.variant-types{gap:8px;margin-bottom:16px}.type-button{padding:12px 9px;gap:9px}.type-icon{width:29px;height:33px;font-size:22px}.type-button strong{font-size:var(--font-body,1rem)}.type-button small{font-size:var(--font-body,1rem)}.play-card{padding:18px 13px}.board-heading{margin-bottom:15px}.board-heading h2{font-size:var(--font-section,1.375rem);font-weight:600}.board-heading .eyebrow{font-size:var(--font-small,.9375rem);letter-spacing:normal}.level-badge{padding:3px 9px;font-size:var(--font-small,.9375rem)}.puzzle-picker{gap:9px;font-size:var(--font-small,.9375rem)}.puzzle-picker label{width:40%}.puzzle-picker select{font-size:var(--font-body,1rem);padding:8px}.rules{font-size:var(--font-small,.9375rem);padding:10px;margin-bottom:16px}.variant-cell{font-size:clamp(21px,6.5vw,30px)}.cell-notes{font-size:clamp(8px,2.2vw,11px);inset:2px}.number-pad{gap:4px}.number-pad button{font-size:20px;padding:8px 0}.play-actions{gap:5px}.play-actions button{font-size:var(--font-body,1rem);min-width:60px;padding:9px 6px}.selection-status{font-size:var(--font-body,1rem)}.keyboard-help{font-size:var(--font-small,.9375rem);line-height:1.9}.practice-sidebar{grid-template-columns:1fr}.practice-sidebar details{grid-column:auto}.puzzle-map{grid-template-columns:repeat(10,minmax(0,1fr))}.side-card{padding:18px}.puzzle-map button{font-size:var(--font-body,1rem)}.feedback{font-size:var(--font-body,1rem)}.variant-board[data-size="4"] .variant-cell{font-size:37px}.variant-board[data-size="6"] .variant-cell{font-size:30px}}

/* Preserve the original rule picker, board, number row and action sequence. */
@media screen and (min-width:861px) and (min-height:560px){
  .topbar{min-height:54px;padding:9px max(20px,calc((100vw - 1340px)/2));gap:16px}
  .topbar nav{gap:18px}
  .brand{font-size:19px}
  .variant-shell{max-width:1340px;padding:12px 22px 24px}
  .page-heading{margin-bottom:10px;gap:20px}
  .page-heading .eyebrow{display:none}
  .page-heading h1{font-size:var(--font-page,1.625rem);line-height:1.4;font-weight:600}
  .page-heading>div>p:last-child{display:none}
  .overall-progress{display:flex;align-items:baseline;gap:8px;padding:6px 12px;min-width:0;border-radius:8px}
  .overall-progress strong{font-size:20px}
  .variant-types{gap:10px;margin-bottom:10px}
  .type-button{padding:7px 11px;gap:9px;border-radius:9px}
  .type-icon{width:31px;height:34px;font-size:22px}
  .type-button strong{font-size:var(--font-body,1rem)}
  .type-button small{margin-top:1px;font-size:var(--font-body,1rem);line-height:1.4}
  .play-card{padding:10px 14px 12px}
  .board-heading{min-height:30px;margin-bottom:7px;align-items:center}
  .board-heading>div{display:flex;flex-wrap:wrap;align-items:baseline;gap:4px 12px}
  .board-heading .eyebrow{margin:0;letter-spacing:normal}
  .board-heading h2{font-size:var(--font-section,1.375rem);font-weight:600}
  .puzzle-picker{gap:12px;margin-bottom:7px}
  .puzzle-picker label{display:flex;align-items:center;gap:8px;white-space:nowrap}
  .puzzle-picker select{min-height:34px;padding:5px 8px;margin:0;flex:1;min-width:0}
  .rules{padding:6px 10px;margin-bottom:8px;line-height:1.5}
  .variant-board{width:min(100%,var(--board-max-size,calc(100dvh - 530px)));max-width:540px;margin:0 auto;container-type:inline-size}
  .variant-cell{font-size:clamp(18px,6.5cqw,34px)}
  .variant-board[data-size="4"] .variant-cell{font-size:clamp(28px,11cqw,42px)}
  .variant-board[data-size="6"] .variant-cell{font-size:clamp(23px,8cqw,34px)}
  .selection-status,.number-pad,.play-actions,.feedback,.progress-track,.keyboard-help{width:min(100%,max(400px,var(--board-max-size,540px)));margin-left:auto;margin-right:auto}
  .selection-status{margin-top:5px;margin-bottom:6px;line-height:1.4}
  .number-pad{grid-template-columns:repeat(var(--size),minmax(0,1fr));gap:4px;margin-bottom:7px}
  .number-pad button{height:44px;padding:4px 0;font-size:22px}
  .play-actions{display:flex;gap:7px;margin-top:0}
  .play-actions button{min-width:0;min-height:36px;padding:5px 6px;font-size:.875rem}
  .feedback{min-height:0;margin-top:7px;line-height:1.55}
  .progress-track{margin-top:6px}
  .keyboard-help{margin-top:7px;line-height:1.5}
}
@media screen and (min-width:861px) and (max-width:1100px) and (min-height:560px){
  .variant-shell{padding:12px 18px 24px}
  .page-heading h1{font-size:var(--font-page,1.625rem);font-weight:600}
  .type-button{padding:7px 8px;gap:7px}
  .type-button small{display:none}
  .topbar nav{gap:12px}
}
@media screen and (min-width:861px) and (min-height:560px) and (max-height:800px){
  .page-heading{margin-bottom:6px}
  .overall-progress{padding:4px 10px;line-height:1.2}
  .overall-progress strong{font-size:18px}
  .variant-types{margin-bottom:6px}
  .type-button{padding-block:5px}
  .type-button strong{font-size:.875rem;line-height:1.25}
  .type-button small{font-size:.75rem;line-height:1.25}
}