:root {
  --ink: #1f2937; --muted: #606b7d; --accent: #2b6cb0; --accent-2: #d97706;
  --bg: #f9fafb; --hilite: #ef4444; --good: #16a34a; --focus: #7c3aed;
  --board-bg: #fff; --border: #e5e7eb; --row-hover: #f8fafc; --row-active: #eef2ff;
  --svg-ink: #111827; --svg-grid: #cbd5e1;
}

body.dark {
  --ink: #f3f4f6; --muted: #9ca3af; --accent: #60a5fa; --accent-2: #fbbf24;
  --bg: #111827; --board-bg: #1f2937; --border: #374151;
  --row-hover: #374151; --row-active: #1e3a8a;
  --svg-ink: #f9fafb; --svg-grid: #4b5563;
}

* { box-sizing: border-box; }

/* keep scroll working normally */
html, body { overflow-x: hidden; overscroll-behavior: auto; }
body {
  font-family: system-ui, Segoe UI, Roboto, Arial, sans-serif;
  margin: 0; background: var(--bg); color: var(--ink);
  transition: background 0.3s, color 0.3s;
}

.header { padding: 1rem 1.25rem; background: var(--board-bg); border-bottom: 1px solid var(--border); }
.header h1 { margin: 0; font-size: 1.6rem; }
.subtitle { margin: .25rem 0 0; color: var(--muted); }

main.layout { display: grid; grid-template-columns: 1fr; gap: 1rem; padding: 1rem; max-width: 1200px; margin: 0 auto; }
@media (min-width: 980px) { main.layout { grid-template-columns: 1fr 1fr; } }

.board, .steps { background: var(--board-bg); border: 1px solid var(--border); border-radius: 8px; padding: .75rem; }
.board { display: flex; flex-direction: column; }
.steps { padding: 1rem; }

.controls { display: flex; gap: .5rem; align-items: center; margin-bottom: .5rem; flex-wrap: wrap; }
button, #mode-select {
  padding: .5rem .75rem; border: 1px solid var(--border); border-radius: 6px;
  background: var(--board-bg); color: var(--ink); cursor: pointer; font-weight: 700;
  transition: all .2s; font-size: 0.9rem;
}
button:hover:not(:disabled), #mode-select:hover { transform: translateY(-2px); box-shadow: 0 4px 6px rgba(0,0,0,.1); }
button.primary { background: var(--accent); color: #fff; border-color: var(--accent); }
button.primary:hover:not(:disabled) { background: #1e40af; }
body.dark button.primary:hover:not(:disabled) { background: #3b82f6; }
button:disabled { opacity: .5; cursor: not-allowed; transform: none; box-shadow: none; }

.muted { color: var(--muted); }
.push-right { margin-left: auto; font-weight: 700; }

.progress-container {
  width: 100%;
  height: 12px;
  background: var(--border);
  border-radius: 6px;
  overflow: hidden;
  margin-bottom: .5rem;
  cursor: pointer;
}
.progress-container:hover { filter: brightness(0.95); }
.progress-container:focus { outline: 2px solid var(--focus); outline-offset: 3px; }
.progress-bar {
  height: 100%;
  width: 0%;
  background: var(--good);
  transition: width .25s cubic-bezier(.4,0,.2,1);
  pointer-events: none;
}

.legend { font-size: .9rem; margin-bottom: .25rem; color: var(--muted); }
#layout-hint { margin: 0 0 .6rem; font-size: .9rem; font-weight: 800; }

.svg-wrapper { position: relative; width: 100%; flex-grow: 1; }

/* scroll fix: do not disable touch actions for entire svg region */
.svg-wrapper, #diagram, #explore-handles { touch-action: auto; }
.handle { touch-action: none; }

svg { width: 100%; height: auto; border-radius: 6px; background: var(--board-bg); display: block; }

.qed-stamp {
  position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%) rotate(-10deg);
  font-size: 4.5rem; font-weight: 900; letter-spacing: 4px; color: rgba(22,163,74,.85);
  border: 8px solid rgba(22,163,74,.85); padding: 1rem 2.5rem; border-radius: 1rem;
  pointer-events: none; backdrop-filter: blur(2px);
  box-shadow: 0 10px 25px rgba(0,0,0,.2), inset 0 0 15px rgba(22,163,74,.3);
  text-shadow: 2px 2px 0 rgba(255,255,255,.5);
}
.stamp-drop { animation: stampDrop .6s cubic-bezier(.175,.885,.32,1.275) forwards; }
@keyframes stampDrop {
  0% { transform:translate(-50%,-50%) scale(3) rotate(-25deg); opacity:0 }
  100% { transform:translate(-50%,-50%) scale(1) rotate(-10deg); opacity:1 }
}

.coach-box {
  margin-top: 0.5rem; padding: 0.85rem 1rem; background: rgba(59, 130, 246, 0.1);
  border-left: 4px solid var(--accent); border-radius: 4px;
  font-size: 1.02rem; line-height: 1.4; min-height: 3.5rem;
  display: flex; flex-direction: column; gap: .5rem;
}
.coach-row { display: flex; align-items: baseline; justify-content: space-between; gap: 1rem; }
.coach-title { font-weight: 900; letter-spacing: .2px; }
.coach-text { margin: 0; }

.mcq {
  border-top: 1px dashed rgba(125,125,125,.4);
  padding-top: .6rem;
  display: grid; gap: .45rem;
}
.mcq h3 { margin: 0; font-size: .98rem; color: var(--ink); }
.mcq .choices { display: grid; gap: .35rem; }
.mcq button.choice {
  text-align: left;
  background: rgba(125,125,125,.06);
  border: 1px solid var(--border);
  padding: .45rem .6rem;
  font-weight: 700;
  border-radius: 8px;
}
.mcq button.choice:hover:not(:disabled) { transform: translateY(-1px); }
.mcq .feedback { font-weight: 900; }
.mcq .feedback.good { color: var(--good); }
.mcq .feedback.bad { color: var(--hilite); }

.guiding { background: var(--row-hover); border: 1px solid var(--border); border-radius: 8px; padding: .75rem .9rem; margin-bottom: 1rem; }
.guiding h2 { margin: .2rem 0 .4rem; font-size: 1.05rem; }

.tchart-wrap { overflow: visible; }
.tchart { width: 100%; border-collapse: collapse; table-layout: fixed; }
.tchart td, .tchart th { overflow-wrap: anywhere; word-break: normal; }
.tchart thead th {
  text-align: left; font-weight: 900; color: var(--accent);
  border-bottom: 2px solid var(--border); padding: .5rem .6rem; background: var(--bg);
  position: sticky; top: 0; z-index: 1;
}
.tchart tbody td { border-bottom: 1px solid var(--border); padding: .8rem .6rem; vertical-align: top; }
.tchart tbody tr {
  cursor: pointer;
  transition: transform .2s cubic-bezier(.4,0,.2,1), background .2s ease, box-shadow .2s ease;
  border-radius: 6px;
}
.tchart tbody tr:hover { background: var(--row-hover); transform: translateX(6px); box-shadow: -4px 0 0 var(--accent-2); }
.tchart tbody tr.active { background: var(--row-active); outline: 2px solid var(--accent); transform: translateX(8px); box-shadow: -6px 0 0 var(--focus); }
.tchart .col-statement { width: 65%; }
.tchart .col-reason { width: 35%; text-align: center; }

.badge {
  display: inline-block; padding: .3rem .6rem; border-radius: .4rem; font-size: .9rem;
  border: 1px solid var(--border); color: #374151; background: #f8fafc; font-weight: 900;
}
body.dark .badge { filter: brightness(0.85); }
.badge.given { color: #0b6b1a; background: #e7f6ea; border-color: #c4e7cb; }
.badge.det { color: #5b21b6; background: #f3e8ff; border-color: #e9d5ff; }
.badge.constr { color: #7a1a0b; background: #fff4ed; border-color: #fde3d3; }
.badge.prop { color: #0b3b6b; background: #e9f2ff; border-color: #d7e7ff; }
.badge.def { color: #0f766e; background: #ecfdf5; border-color: #bbf7d0; }
.badge.thus { color: #065f46; background: #ecfdf5; border-color: #d1fae5; }

.has-tooltip { cursor: help; text-decoration: underline dotted var(--muted); }
.has-tooltip:focus { outline: 2px solid var(--focus); outline-offset: 2px; }

#floating-tooltip {
  position: fixed;
  z-index: 999999;
  max-width: 340px;
  padding: 8px 10px;
  border-radius: 10px;
  background: rgba(15, 23, 42, 0.96);
  color: white;
  font-size: 14px;
  line-height: 1.25;
  box-shadow: 0 10px 30px rgba(0,0,0,0.35);
  pointer-events: none;
  display: none;
}
body.dark #floating-tooltip { background: rgba(2, 6, 23, 0.96); }

.geom-ref { font-weight: 900; cursor: pointer; color: var(--accent); transition: color 0.2s, background 0.2s; border-radius: 3px; padding: 0 2px; }
.geom-ref:hover { color: var(--hilite); background: rgba(239, 68, 68, 0.15); }

.practice-select {
  width: 100%; max-width: 100%; padding: 0.4rem; margin-bottom: 0.4rem; border-radius: 4px;
  border: 2px solid var(--accent); background: var(--board-bg); color: var(--ink);
  font-weight: 900; cursor: pointer;
  white-space: normal; height: auto; word-break: break-word;
}
.blur-hidden { filter: blur(5px); opacity: 0.5; pointer-events: none; user-select: none; transition: filter 0.3s; }

.hidden { opacity: 0 !important; visibility: hidden !important; pointer-events: none !important; }
.fade-in { animation: fade .25s ease-out forwards; }
@keyframes fade { from{opacity:0} to{opacity:1} }
.draw-solid { stroke-dasharray: 2000; stroke-dashoffset: 2000; animation: drawLine .9s ease-in-out forwards; }
@keyframes drawLine { to{stroke-dashoffset:0} }

.tick { stroke-linecap: round; }
@keyframes flashHighlight { 0%{filter:drop-shadow(0 0 12px var(--focus))} 100%{filter:drop-shadow(0 0 2px rgba(0,0,0,.3))} }

:is(line, path, polygon, circle, rect).highlight {
  animation: flashHighlight .45s ease-out;
  filter: drop-shadow(0 0 2px rgba(0,0,0,.3));
}
:is(line, path, polygon, circle, rect).hl-strong { stroke: var(--accent-2)!important; stroke-width: 5!important; }
:is(line, path, polygon, circle, rect).hl-parallelogram { stroke: var(--accent-2)!important; stroke-width: 4!important; fill: rgba(217,119,6,.08)!important; }
:is(line, path, polygon, circle, rect).hl-tri { stroke: var(--good)!important; stroke-width: 4!important; fill: rgba(22,163,74,.10)!important; }

g.hl-strong :is(line, path, polygon, circle, rect) { stroke: var(--accent-2)!important; stroke-width: 5!important; }
g.hl-parallelogram :is(line, path, polygon, circle, rect) { stroke: var(--accent-2)!important; stroke-width: 4!important; fill: rgba(217,119,6,.08)!important; }
g.hl-tri :is(line, path, polygon, circle, rect) { stroke: var(--good)!important; stroke-width: 4!important; fill: rgba(22,163,74,.10)!important; }

text.hl-strong, text.hl-parallelogram { fill: var(--accent-2)!important; stroke: none!important; }
text.hl-tri { fill: var(--good)!important; stroke: none!important; }
text.highlight { filter: none !important; }

.hover-hl { stroke: var(--hilite) !important; stroke-width: 5 !important; filter: drop-shadow(0 0 6px rgba(239, 68, 68, 0.8)) !important; fill: rgba(239, 68, 68, 0.15) !important; transition: all 0.2s; }
text.hover-hl { fill: var(--hilite) !important; stroke: none !important; filter: none !important; }
g.hover-hl :is(line, path, polygon, circle, rect) { stroke: var(--hilite) !important; stroke-width: 5 !important; filter: drop-shadow(0 0 6px rgba(239, 68, 68, 0.8)) !important; fill: rgba(239, 68, 68, 0.15) !important; }
g.hover-hl text { fill: var(--hilite) !important; stroke: none !important; filter: none !important; }

svg :is(line, path, polygon, circle, rect, text) { transition: opacity .25s ease; }
svg.focusless :is(line, path, polygon, circle, rect, text) { opacity: .12; }
svg.focusless #labels text { opacity: 1 !important; }
svg.focusless :is(line, path, polygon, circle, rect, text).highlight,
svg.focusless :is(line, path, polygon, circle, rect, text).hover-hl { opacity: 1 !important; }
svg.focusless :is(g.highlight, g.hover-hl) :is(line, path, polygon, circle, rect, text) { opacity: 1 !important; }
svg.focusless .focus-keep { opacity: .35 !important; }
svg.focusless g.focus-keep :is(line, path, polygon, circle, rect, text) { opacity: .35 !important; }

[tabindex="0"]:focus { outline: 2px solid var(--focus); outline-offset: 2px; }
.sr-only {
  position: absolute !important; width: 1px !important; height: 1px !important; padding: 0 !important;
  margin: -1px !important; overflow: hidden !important; clip: rect(0,0,0,0) !important; white-space: nowrap !important; border: 0 !important;
}

.handle { fill: rgba(124,58,237,.22); stroke: rgba(124,58,237,.8); stroke-width: 2; cursor: grab; }
.handle:active { cursor: grabbing; }
.handle-ring { fill: none; stroke: rgba(124,58,237,.35); stroke-width: 6; }

.modal {
  position: fixed; inset: 0;
  background: rgba(0,0,0,.55);
  display: flex; align-items: center; justify-content: center;
  padding: 1rem;
  z-index: 9999;
}
.modal.hidden { display: none !important; }

.modal-card {
  width: min(720px, 92vw);
  background: var(--board-bg);
  color: var(--ink);
  border: 1px solid var(--border);
  border-radius: 12px;
  box-shadow: 0 18px 55px rgba(0,0,0,.35);
  padding: 1rem 1.1rem;
}
.modal-head { display:flex; align-items:center; justify-content:space-between; gap:1rem; }
.modal-head h2 { margin:0; font-size:1.2rem; }
.modal-body { margin-top:.75rem; line-height:1.5; }
.modal-body ul { margin:.6rem 0 0 1.2rem; }

@media (prefers-reduced-motion: reduce) { * { animation: none!important; transition: none!important; scroll-behavior: auto!important; } }
@media print { .controls, .guiding, .progress-container { display: none; } }