:root{--navy:#071d31;--navy2:#0b2843;--ink:#09213d;--cyan:#43ddff;--line:#2b4c68;--gold:#f0bf22;--paper:#eef5fb;--muted:#83baf0;--white:#fff}
*{box-sizing:border-box}body{margin:0;background:linear-gradient(180deg,#f3f8fc,#eaf2f9);color:var(--ink);font-family:Inter,ui-sans-serif,system-ui,-apple-system,"Segoe UI",sans-serif}.page-shell{max-width:1760px;margin:auto;padding:28px}.hero{display:flex;align-items:flex-start;justify-content:space-between;gap:24px;margin-bottom:22px}.eyebrow{margin:0 0 8px;font-size:14px;font-weight:900;letter-spacing:.14em;color:#2b74b8}.hero h1{font-size:clamp(30px,4vw,52px);margin:0 0 8px;line-height:1.05}.intro{max-width:850px;font-size:18px;color:#45617c;margin:0}.back-link{background:#fff;border:1px solid #c7d8e8;border-radius:12px;padding:12px 16px;text-decoration:none;color:#31516f;font-weight:800}.workspace{display:grid;gap:22px}.editor-card,.trace-lab{background:#fff;border:1px solid #c9d9e7;border-radius:22px;box-shadow:0 18px 45px rgba(27,68,104,.1);overflow:hidden}.editor-card{padding:20px}.section-head,.run-row{display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap}.section-head{margin-bottom:12px;font-size:18px}.step-badge{display:inline-grid;place-items:center;width:28px;height:28px;border-radius:50%;background:var(--gold);color:#071d31;margin-right:8px;font-weight:900}textarea{width:100%;resize:vertical;border:1px solid #bdd2e4;border-radius:14px;background:#061a2b;color:#edf8ff;font:600 15px/1.55 "Cascadia Code","SFMono-Regular",Consolas,monospace;padding:16px;outline:none}#codeInput{min-height:330px}#stdinInput{min-height:78px;margin-top:8px}.input-row{margin-top:16px}.input-row label{font-weight:850}.input-row small{font-weight:600;color:#7189a0}.run-row{justify-content:flex-start;margin-top:16px}.run-row button,.controls button,.section-head button{border:1px solid #2f5676;border-radius:12px;padding:11px 18px;font-weight:900;cursor:pointer}.primary,.gold{background:var(--gold)!important;color:#06182a!important;border-color:var(--gold)!important}.secondary,.controls button{background:#103553;color:#fff}.step-limit{margin-left:auto;font-weight:750;color:#45617c}.step-limit input{width:90px;margin-left:8px;padding:9px;border:1px solid #bdd2e4;border-radius:9px}.support-note{color:#607b94;margin:14px 0 0;font-size:14px}.error-box{margin-top:14px;padding:14px 16px;border-radius:12px;background:#fff0f0;border:1px solid #f2b5b5;color:#992828;font-weight:700}.trace-lab{background:var(--navy);color:white}.trace-toolbar{display:flex;justify-content:space-between;gap:20px;align-items:center;padding:20px 22px;border-bottom:1px solid var(--line)}.trace-toolbar .eyebrow{color:#90c7ff}.trace-toolbar h2{margin:0;font:800 20px Georgia,serif}.trace-toolbar p{margin:5px 0 0;color:#8ecbff}.controls{display:flex;gap:10px;flex-wrap:wrap;justify-content:flex-end}.controls button:disabled{opacity:.35;cursor:not-allowed}.trace-grid{display:grid;grid-template-columns:minmax(0,1.7fr) minmax(500px,1.15fr);min-height:520px}.source-pane{background:#031526;border-right:1px solid var(--line);padding:18px 0;max-height:62vh;min-height:480px;overflow:auto;overscroll-behavior:contain;scrollbar-gutter:stable;font:700 16px/1.75 "Cascadia Code",Consolas,monospace}.code-line{display:grid;grid-template-columns:58px 1fr;min-width:max-content;padding-right:24px}.line-no{color:#6b9bc8;text-align:right;padding-right:18px;user-select:none}.line-text{white-space:pre}.code-line.active{background:#154566;border-left:4px solid var(--gold)}.code-line.active .line-no{color:var(--gold);font-weight:900}.state-pane{background:#082238;max-height:62vh;overflow:auto}.state-pane section{padding:18px 20px;border-bottom:1px solid var(--line)}.state-pane h3{margin:0 0 12px;color:var(--cyan);font-size:15px;letter-spacing:.06em}.state-pane p{margin:0;line-height:1.55}.table-wrap{overflow:auto}table{width:100%;border-collapse:collapse;font-size:14px}th,td{border:1px solid #31536d;padding:10px;text-align:left}th{color:#85bdf0;background:#0c2d48}.stack-list{display:flex;gap:8px;flex-wrap:wrap}.stack-chip{border:1px solid #3e7198;border-radius:9px;padding:7px 10px;background:#103b5b;font:700 13px Consolas,monospace}.stack-arrow{align-self:center;color:#a8d5f8}pre{margin:0;min-height:100px;background:#031526;padding:16px;border-radius:4px;color:#eeffd8;white-space:pre-wrap;font:700 14px/1.6 Consolas,monospace}.trace-footer{display:flex;align-items:center;gap:16px;padding:12px 18px;background:#0a2a46}.trace-footer progress{flex:1;accent-color:var(--gold)}.trace-footer span{font-weight:800;white-space:nowrap}.flash{animation:flash .6s ease}@keyframes flash{50%{box-shadow:inset 0 0 0 2px var(--gold)}}
@media(max-width:980px){.page-shell{padding:12px}.hero,.trace-toolbar{flex-direction:column;align-items:stretch}.trace-grid{grid-template-columns:1fr}.source-pane{border-right:0;border-bottom:1px solid var(--line);max-height:50vh;min-height:360px}.state-pane{max-height:none}.controls{justify-content:flex-start}.step-limit{margin-left:0}.back-link{align-self:flex-start}}
/* Phase 5: command-line argument field uses the same CodeBhavya tracer treatment. */
.input-row input[type="text"]{width:100%;box-sizing:border-box;background:#061d2d;color:#fff;border:1px solid #37627d;border-radius:10px;padding:12px 14px;font:inherit;outline:none}.input-row input[type="text"]:focus{border-color:#f5c322;box-shadow:0 0 0 2px rgba(245,195,34,.12)}

/* Phase 7: live memory + DSA visualization. */
.visual-title-row{display:flex;align-items:center;justify-content:space-between;gap:10px}.visual-title-row h3{margin-bottom:0}.visual-mode{font-size:11px;font-weight:900;letter-spacing:.08em;border:1px solid #3f7198;background:#103b5b;color:#9ddcff;border-radius:999px;padding:4px 8px}.dsa-visualizer{margin-top:12px;display:grid;gap:14px}.visual-empty{color:#91b9d8!important;font-size:13px}.viz-block{background:#041a2c;border:1px solid #294f6d;border-radius:12px;padding:12px}.viz-block-title{display:flex;align-items:center;justify-content:space-between;gap:8px;margin-bottom:10px;color:#d7f5ff;font-size:12px;font-weight:900;letter-spacing:.05em}.viz-subtle{color:#82aeca;font-size:11px;font-weight:700}.pointer-row,.array-row{display:flex;flex-wrap:wrap;gap:7px;align-items:center}.pointer-chip,.array-cell{border:1px solid #3d7198;background:#0d3553;border-radius:8px;padding:7px 9px;font:700 12px "Cascadia Code",Consolas,monospace}.pointer-chip strong{color:#ffd23f}.array-cell{min-width:44px;text-align:center;position:relative}.array-cell .idx{display:block;color:#6ea9d6;font-size:9px;margin-bottom:2px}.heap-grid{display:flex;flex-wrap:wrap;gap:10px}.heap-card{min-width:150px;max-width:260px;border:1px solid #3b6e94;background:#0a304c;border-radius:11px;padding:10px;font:700 11px/1.5 "Cascadia Code",Consolas,monospace}.heap-card.freed{opacity:.55;border-style:dashed}.heap-address{color:#ffd23f;font-weight:900;margin-bottom:5px}.heap-field{display:flex;gap:6px;justify-content:space-between;border-top:1px solid rgba(137,196,235,.14);padding-top:4px;margin-top:4px}.heap-field .field-name{color:#8ddfff}.heap-ref{color:#b8ff9e}.chain{display:flex;align-items:center;gap:8px;overflow:auto;padding-bottom:4px}.chain-node{flex:0 0 auto;min-width:110px;border:2px solid #3f82ad;background:#0b3a59;border-radius:12px;padding:9px;text-align:center}.chain-node .addr{font:800 10px Consolas,monospace;color:#80c8f5}.chain-node .data{font:900 15px Consolas,monospace;color:#fff;margin-top:4px}.chain-arrow{flex:0 0 auto;color:#ffd23f;font-size:22px;font-weight:900}.null-node{flex:0 0 auto;border:1px dashed #6388a2;color:#91aebe;border-radius:8px;padding:7px 10px;font:800 11px Consolas,monospace}.tree-wrap{overflow:auto;padding:4px}.tree-level{display:flex;justify-content:center;gap:20px;margin:10px 0}.tree-node{min-width:88px;background:#0c3b59;border:2px solid #3d84ae;border-radius:50px;padding:9px 12px;text-align:center;font:800 11px Consolas,monospace}.tree-node .tree-data{font-size:14px;color:#fff}.tree-node .tree-addr{font-size:9px;color:#80c8f5}.queue-strip{display:flex;gap:6px;overflow:auto;padding:4px 0}.queue-cell{min-width:54px;border:1px solid #3d7198;background:#0d3553;border-radius:8px;text-align:center;padding:8px 6px;position:relative;font:800 12px Consolas,monospace}.queue-mark{position:absolute;top:-11px;left:50%;transform:translateX(-50%);font-size:8px;color:#ffd23f;font-weight:900;white-space:nowrap}.visual-section{min-height:140px}
@media(max-width:980px){.heap-card{max-width:100%;}.chain-node{min-width:100px}.visual-section{min-height:auto}}


/* Phase 7.1: smart state focus + current-change highlighting, matching the Java tracer UX. */
.state-pane{scroll-behavior:smooth;overflow-anchor:none}
.state-pane section{padding:13px 16px;overflow-anchor:none}
.state-pane h3{margin-bottom:9px;font-size:15px}
.state-pane .table-wrap{max-height:165px;overflow:auto;scrollbar-width:thin;scroll-behavior:smooth;overscroll-behavior:contain;overflow-anchor:none}
.state-pane table{font-size:13px}
.state-pane th,.state-pane td{padding:8px 10px}
#variablesBody tr.var-changed td{background:rgba(240,191,34,.36);color:#fff7cf;border-color:#d7a900}
#variablesBody tr.var-changed td:last-child{color:#ffe15a;font-weight:950}
.visual-section{min-height:0}
.dsa-visualizer{gap:10px;margin-top:10px;overflow-anchor:none}
.viz-block{padding:10px;scroll-margin-block:12px;transition:border-color .2s,box-shadow .2s,background .2s}
.viz-block.visual-changed{border-color:#f0bf22;box-shadow:0 0 0 2px rgba(240,191,34,.18);background:#12364b;animation:statePulse .75s ease}
.pointer-chip.visual-changed,.heap-card.visual-changed{border-color:#f0bf22;box-shadow:0 0 0 2px rgba(240,191,34,.2);animation:statePulse .75s ease}
.array-cell.cell-changed,.queue-cell.cell-changed{background:#f7df7c!important;color:#2f2600!important;border-color:#f0bf22!important;box-shadow:0 0 0 2px rgba(240,191,34,.18)}
.array-cell.cell-changed .idx{color:#5f4a00!important}
@keyframes statePulse{0%{filter:brightness(1.5)}100%{filter:brightness(1)}}
.pointer-row,.array-row,.chain,.queue-strip,.tree-wrap,.heap-grid{overscroll-behavior:contain;scroll-behavior:smooth}
@media(max-width:980px){.state-pane .table-wrap{max-height:180px}}

/* Phase 7.1: algorithm-aware array visualization */
.array-action{display:flex;flex-wrap:wrap;align-items:center;gap:8px;margin:-2px 0 10px;padding:6px 8px;border-radius:8px;background:rgba(65,146,196,.10);border:1px solid rgba(91,169,219,.22);color:#9edcff;font:800 10px/1.3 "Cascadia Code",Consolas,monospace;letter-spacing:.03em}
.pivot-info{margin-left:auto;color:#ffd23f;border:1px solid rgba(255,210,63,.38);border-radius:999px;padding:2px 7px;background:rgba(255,210,63,.08)}
.array-cell.range-active{border-color:#5ca9d8;background:#0e3e60;box-shadow:inset 0 0 0 1px rgba(92,169,216,.14)}
.array-cell.cell-swap{background:#ffd95d!important;color:#2d2400!important;border-color:#fff0a1!important;box-shadow:0 0 0 2px rgba(255,217,93,.28);animation:statePulse .8s ease}
.array-cell.cell-swap .idx{color:#6b5200!important}
.array-cell.cell-swap::after{content:"SWAP";position:absolute;right:-3px;bottom:-9px;font:900 7px/1 Arial,sans-serif;letter-spacing:.06em;color:#2d2400;background:#ffd95d;border-radius:999px;padding:2px 4px;border:1px solid #fff0a1}
.array-markers{position:absolute;left:50%;bottom:calc(100% + 4px);transform:translateX(-50%);display:flex;gap:2px;z-index:2;white-space:nowrap}
.array-marker{display:inline-block;padding:2px 5px;border-radius:999px;background:#f2bf25;color:#172434;border:1px solid #ffe68d;font:900 8px/1 Arial,sans-serif;box-shadow:0 1px 4px rgba(0,0,0,.25)}
.array-row{padding-top:20px}
.array-value{display:block}

/* Phase 7.1: algorithm-aware array visualization */
.array-action{display:flex;flex-wrap:wrap;align-items:center;gap:8px;margin:-2px 0 10px;padding:6px 8px;border-radius:8px;background:rgba(65,146,196,.10);border:1px solid rgba(91,169,219,.22);color:#9edcff;font:800 10px/1.3 "Cascadia Code",Consolas,monospace;letter-spacing:.03em}
.pivot-info{margin-left:auto;color:#ffd23f;border:1px solid rgba(255,210,63,.38);border-radius:999px;padding:2px 7px;background:rgba(255,210,63,.08)}
.array-cell.range-active{border-color:#5ca9d8;background:#0e3e60;box-shadow:inset 0 0 0 1px rgba(92,169,216,.14)}
.array-cell.cell-swap{background:#ffd95d!important;color:#2d2400!important;border-color:#fff0a1!important;box-shadow:0 0 0 2px rgba(255,217,93,.28);animation:statePulse .8s ease}
.array-cell.cell-swap .idx{color:#6b5200!important}
.array-cell.cell-swap::after{content:"SWAP";position:absolute;right:-3px;bottom:-9px;font:900 7px/1 Arial,sans-serif;letter-spacing:.06em;color:#2d2400;background:#ffd95d;border-radius:999px;padding:2px 4px;border:1px solid #fff0a1}
.array-markers{position:absolute;left:50%;bottom:calc(100% + 4px);transform:translateX(-50%);display:flex;gap:2px;z-index:2;white-space:nowrap}
.array-marker{display:inline-block;padding:2px 5px;border-radius:999px;background:#f2bf25;color:#172434;border:1px solid #ffe68d;font:900 8px/1 Arial,sans-serif;box-shadow:0 1px 4px rgba(0,0,0,.25)}
.array-row{padding-top:20px}
.array-value{display:block}

/* Phase 7.2: clearer algorithm markers and roomier right pane */
.array-row{gap:10px;padding-top:30px;padding-inline:2px;overflow-x:auto;overflow-y:visible}
.array-cell{min-width:52px;min-height:56px;padding:10px 10px 9px;border-width:2px;display:flex;flex-direction:column;justify-content:center;align-items:center;gap:2px;overflow:visible}
.array-cell.marker-target{border-color:#8fd6ff;box-shadow:0 0 0 2px rgba(100,186,242,.15), inset 0 0 0 1px rgba(143,214,255,.15)}
.array-cell.marker-target.range-active{border-color:#49c7ff;box-shadow:0 0 0 2px rgba(73,199,255,.20), inset 0 0 0 1px rgba(73,199,255,.15)}
.array-cell .idx{font-size:10px;font-weight:900}
.array-value{display:block;font-size:16px;font-weight:900;line-height:1.1;color:#fff}
.array-markers{position:absolute;left:50%;bottom:calc(100% + 6px);transform:translateX(-50%);display:flex;flex-wrap:wrap;justify-content:center;gap:4px;z-index:2;white-space:nowrap;max-width:120px}
.array-marker{display:inline-flex;align-items:center;justify-content:center;min-width:24px;padding:3px 7px;border-radius:999px;font:900 9px/1 Arial,sans-serif;letter-spacing:.04em;color:#172434;border:1px solid rgba(255,255,255,.55);box-shadow:0 2px 8px rgba(0,0,0,.28)}
.array-marker.marker-i,.array-marker.marker-j,.array-marker.marker-k,.array-marker.marker-left,.array-marker.marker-right{background:#8be9fd;color:#072336;border-color:#c7fbff}
.array-marker.marker-low,.array-marker.marker-high,.array-marker.marker-mid,.array-marker.marker-pi,.array-marker.marker-pivotindex,.array-marker.marker-pivot,.array-marker.marker-smaller{background:#ffd761;color:#312400;border-color:#fff0b4}
.array-marker.marker-front,.array-marker.marker-rear,.array-marker.marker-top{background:#98f5a5;color:#0f2e17;border-color:#d1ffd6}
.array-cell.marker-target.cell-changed,.array-cell.marker-target.cell-swap{box-shadow:0 0 0 3px rgba(240,191,34,.26)}
@media (max-width: 1280px){.trace-grid{grid-template-columns:minmax(0,1.55fr) minmax(440px,1.1fr)}.array-cell{min-width:48px}.array-value{font-size:15px}}

/* Phase 7.2.1: keep algorithm index markers fully visible */
.viz-block{overflow:visible}
.array-row{padding-top:42px!important;overflow-x:auto;overflow-y:visible!important}
.array-markers{bottom:calc(100% + 2px)!important;top:auto!important;max-width:150px!important;row-gap:4px}
.array-marker{position:relative;z-index:3}
.array-action + .array-row{margin-top:2px}


/* CodeBhavya numbered source editor: line numbers remain aligned while students type/scroll. */
.code-editor-numbered{
  display:flex;
  align-items:stretch;
  width:100%;
  overflow:hidden;
  border:1px solid #bdd2e4;
  border-radius:14px;
  background:#061a2b;
}
.code-editor-numbered:focus-within{
  border-color:#5aa7df;
  box-shadow:0 0 0 2px rgba(90,167,223,.12);
}
.code-editor-numbered #codeInput{
  flex:1 1 auto;
  min-width:0;
  width:auto;
  margin:0;
  border:0!important;
  border-radius:0!important;
  outline:0!important;
  box-shadow:none!important;
  background:#061a2b!important;
  overflow:auto;
  white-space:pre;
}
.code-line-numbers{
  flex:0 0 auto;
  min-width:54px;
  height:auto;
  overflow:hidden;
  padding:16px 10px 16px 6px;
  border-right:1px solid #284964;
  background:#071d31;
  color:#6fa8d7;
  text-align:right;
  user-select:none;
  pointer-events:none;
  font:700 15px/1.55 "Cascadia Code","SFMono-Regular",Consolas,monospace;
}
.code-line-number{
  display:block;
  height:1.55em;
  line-height:1.55em;
  padding:0 5px;
  border-radius:5px;
}
.code-line-number.error-line{
  background:#7b2630;
  color:#fff4f4;
  font-weight:950;
  box-shadow:inset 3px 0 0 #ff5b69;
}
@media(max-width:700px){
  .code-line-numbers{min-width:44px;padding-left:3px;padding-right:7px;font-size:13px}
  .code-editor-numbered #codeInput{font-size:13px}
}


/* Mobile execution source guard: keep the traced program visible while stepping. */
@media (max-width:980px){
  #traceLab .trace-grid{display:grid !important;grid-template-columns:minmax(0,1fr) !important;}
  #traceLab #sourcePane.source-pane{
    display:block !important;
    visibility:visible !important;
    width:100% !important;
    min-width:0 !important;
    min-height:320px !important;
    height:46vh !important;
    max-height:520px !important;
    overflow:auto !important;
    order:0 !important;
    border-right:0 !important;
    border-bottom:1px solid var(--line) !important;
    -webkit-overflow-scrolling:touch;
  }
  #traceLab .state-pane{order:1 !important;width:100% !important;min-width:0 !important;}
}
@media (max-width:520px){
  #traceLab #sourcePane.source-pane{min-height:280px !important;height:42vh !important;}
  #traceLab .code-line{grid-template-columns:46px max-content;min-width:100%;padding-right:16px;}
  #traceLab .line-no{padding-right:12px;}
}