/* qistyna-math — exercise-book design system
   Graph-paper surface, ink text, ballpoint-blue actions, highlighter streaks,
   teacher's tick green / gentle correction orange. System fonts only. */

:root {
  --paper: #FAFBF7;
  --grid: #E4EAE2;
  --card: #FFFFFF;
  --ink: #22324A;
  --ink-2: #5A6B84;
  --ink-3: #93A1B5;
  --pen: #3B5BDB;
  --pen-soft: #E8EDFB;
  --hl: #FFD43B;
  --hl-soft: #FFF3BF;
  --tick: #2F9E44;
  --tick-soft: #E6F4E8;
  --cross: #E8590C;
  --cross-soft: #FDEEE3;
  --track: #E9EDF2;
  --shadow: 0 1px 3px rgba(34, 50, 74, 0.08), 0 4px 14px rgba(34, 50, 74, 0.06);
  --radius: 14px;
  --math-font: Georgia, 'Times New Roman', serif;
  --ui-font: system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
}
@media (prefers-color-scheme: dark) {
  :root {
    --paper: #101827;
    --grid: #1A2334;
    --card: #182234;
    --ink: #E7ECF4;
    --ink-2: #A5B1C4;
    --ink-3: #6B7A92;
    --pen: #5C7CFA;
    --pen-soft: #232F4C;
    --hl: #FFD43B;
    --hl-soft: #3D3517;
    --tick: #40C057;
    --tick-soft: #14301C;
    --cross: #FF8A3D;
    --cross-soft: #3A2313;
    --track: #243048;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.4);
  }
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { -webkit-text-size-adjust: 100%; }
body {
  font-family: var(--ui-font);
  background-color: var(--paper);
  /* the graph-paper signature: faint 22px grid, pure CSS */
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 22px 22px;
  color: var(--ink);
  min-height: 100vh; /* Safari < 15.4 fallback */
  min-height: 100dvh;
  line-height: 1.5;
  padding-bottom: calc(64px + env(safe-area-inset-bottom));
}

#app { max-width: 560px; margin: 0 auto; padding: 16px 14px 24px; }

h1, h2, h3 { line-height: 1.25; }
.screen-title { font-size: 1.35rem; font-weight: 800; letter-spacing: -0.02em; margin: 6px 0 2px; }
.screen-sub { color: var(--ink-2); font-size: 0.92rem; margin-bottom: 14px; }

/* ---- math rendering ------------------------------------------------------ */
.math { font-family: var(--math-font); font-size: 1.12em; }
.mfrac {
  display: inline-flex; flex-direction: column; align-items: center;
  vertical-align: middle; margin: 0 0.15em; line-height: 1.15;
}
.mfrac > .num { padding: 0 0.3em 0.08em; }
.mfrac > .den { padding: 0.08em 0.3em 0; border-top: 1.5px solid currentColor; }
sup { font-size: 0.72em; }
.mblock { display: block; white-space: pre-wrap; }

/* ---- cards --------------------------------------------------------------- */
.card {
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 18px 16px;
  margin-bottom: 14px;
  position: relative;
  overflow: hidden;
}
.qcard .chapter-tag {
  display: inline-block; font-size: 0.72rem; font-weight: 700;
  letter-spacing: 0.04em; text-transform: uppercase;
  color: var(--pen); background: var(--pen-soft);
  border-radius: 6px; padding: 2px 8px; margin-bottom: 10px;
}
.qcard .qtext { font-size: 1.06rem; line-height: 1.65; }
.qcard .qtext .math { font-size: 1.22em; }

/* graph area */
.qgraph { margin: 12px 0 4px; text-align: center; }
.qgraph svg { max-width: 100%; height: auto; }
.qgraph .svggrid { stroke: var(--grid); stroke-width: 1; }
.qgraph .svgaxis { stroke: var(--ink-2); stroke-width: 1.4; }
.qgraph .svgline { stroke: var(--pen); stroke-width: 2.4; fill: none; }
.qgraph .svgline2 { stroke: var(--cross); stroke-width: 2.4; fill: none; }
.qgraph .svgpt { fill: var(--ink); }
.qgraph .svgbar { fill: var(--pen); opacity: 0.85; }
.qgraph text { fill: var(--ink-2); font-size: 11px; font-family: var(--ui-font); }

/* ---- answer input -------------------------------------------------------- */
.answer-row { display: flex; gap: 8px; align-items: stretch; margin-top: 14px; }
.answer-label { align-self: center; color: var(--ink-2); font-family: var(--math-font); white-space: nowrap; }
input.answer {
  flex: 1; min-width: 0;
  font-family: var(--math-font); font-size: 1.15rem;
  padding: 12px 14px; color: var(--ink);
  background: var(--paper); border: 2px solid var(--track);
  border-radius: 10px; outline: none;
}
input.answer:focus { border-color: var(--pen); }
input.answer.wrong { border-color: var(--cross); animation: shake 0.3s; }
@keyframes shake { 25% { transform: translateX(-4px); } 75% { transform: translateX(4px); } }

/* live preview of typed maths — the "did I type what I meant?" mirror */
.preview {
  min-height: 34px; margin-top: 8px; padding: 6px 10px;
  color: var(--ink-2); font-size: 0.85rem;
  display: flex; align-items: center; gap: 8px;
}
.preview .math { color: var(--ink); font-size: 1.25rem; }
.preview:empty { display: none; }

/* key strip: math symbols above the keyboard */
.keystrip {
  display: flex; gap: 6px; overflow-x: auto; padding: 8px 0 2px;
  -webkit-overflow-scrolling: touch; scrollbar-width: none;
}
.keystrip::-webkit-scrollbar { display: none; }
.keystrip button {
  font-family: var(--math-font); font-size: 1.05rem;
  min-width: 42px; height: 40px; padding: 0 10px;
  border: 1.5px solid var(--track); border-radius: 9px;
  background: var(--card); color: var(--ink);
  flex-shrink: 0;
}
.keystrip button:active { background: var(--pen-soft); border-color: var(--pen); }

/* MCQ choices */
.choices { display: flex; flex-direction: column; gap: 9px; margin-top: 14px; }
.choices button {
  text-align: left; font-size: 1rem; font-family: var(--math-font);
  padding: 13px 14px; border-radius: 10px;
  border: 2px solid var(--track); background: var(--card); color: var(--ink);
}
.choices button.sel { border-color: var(--pen); background: var(--pen-soft); }
.choices button.right { border-color: var(--tick); background: var(--tick-soft); }
.choices button.wrongpick { border-color: var(--cross); background: var(--cross-soft); }

/* ---- buttons -------------------------------------------------------------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  font-family: var(--ui-font); font-size: 1rem; font-weight: 700;
  padding: 13px 18px; border-radius: 11px; border: none;
  background: var(--pen); color: #fff; width: 100%;
  touch-action: manipulation;
}
.btn:active { transform: translateY(1px); }
.btn:disabled { opacity: 0.45; }
.btn.ghost { background: transparent; color: var(--pen); border: 2px solid var(--pen-soft); }
.btn.small { width: auto; padding: 8px 14px; font-size: 0.88rem; }

/* grade buttons (RemNote-style) */
.grades { display: grid; grid-template-columns: repeat(4, 1fr); gap: 7px; margin-top: 12px; }
.grades button {
  padding: 11px 4px 8px; border-radius: 10px; border: none;
  font-weight: 700; font-size: 0.9rem; color: #fff;
}
.grades .g-int { display: block; font-weight: 400; font-size: 0.7rem; opacity: 0.85; margin-top: 1px; }
.g0 { background: var(--cross); }
.g1 { background: #E8A33D; }
.g2 { background: var(--tick); }
.g3 { background: var(--pen); }

/* ---- feedback / marking ---------------------------------------------------- */
.markwrap { position: absolute; top: 8px; right: 10px; width: 46px; height: 46px; pointer-events: none; }
.tickpath {
  stroke: var(--tick); stroke-width: 5; fill: none;
  stroke-linecap: round; stroke-linejoin: round;
  stroke-dasharray: 60; stroke-dashoffset: 60;
  animation: drawtick 0.4s ease-out forwards;
}
@keyframes drawtick { to { stroke-dashoffset: 0; } }
.feedback { margin-top: 12px; padding: 12px 14px; border-radius: 10px; font-size: 0.95rem; }
.feedback.good { background: var(--tick-soft); color: var(--tick); font-weight: 700; }
.feedback.almost { background: var(--hl-soft); color: var(--ink); }
.feedback.notyet { background: var(--cross-soft); color: var(--ink); }

/* worked steps */
.steps { margin-top: 12px; border-top: 1.5px dashed var(--track); padding-top: 12px; }
.steps .step { display: flex; gap: 10px; margin-bottom: 9px; font-size: 0.96rem; line-height: 1.6; }
.steps .stepno {
  flex-shrink: 0; width: 22px; height: 22px; margin-top: 2px;
  border-radius: 50%; background: var(--pen-soft); color: var(--pen);
  font-size: 0.75rem; font-weight: 700; display: flex; align-items: center; justify-content: center;
}

/* hint box */
.hintbox { margin-top: 10px; padding: 11px 13px; background: var(--hl-soft); border-radius: 10px; font-size: 0.93rem; }
.hintbox::before { content: '💡 '; }

/* ---- today / queue -------------------------------------------------------- */
.hero {
  background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 18px 16px; margin-bottom: 14px;
  display: flex; align-items: center; gap: 14px;
}
.hero .flame { font-size: 2rem; }
.hero .streak-n { font-size: 1.6rem; font-weight: 800; line-height: 1.1; }
.hero .streak-n em {
  font-style: normal;
  background: linear-gradient(transparent 55%, var(--hl) 55%, var(--hl) 92%, transparent 92%);
}
.hero .streak-sub { color: var(--ink-2); font-size: 0.85rem; }
.wa3-pill {
  margin-left: auto; text-align: center; background: var(--pen-soft);
  border-radius: 10px; padding: 8px 12px;
}
.wa3-pill .n { font-size: 1.15rem; font-weight: 800; color: var(--pen); }
.wa3-pill .l { font-size: 0.68rem; color: var(--ink-2); }

.progressbar { height: 8px; background: var(--track); border-radius: 4px; overflow: hidden; margin: 10px 0 4px; }
.progressbar > div { height: 100%; background: var(--pen); border-radius: 4px; transition: width 0.3s; }

/* ---- chapter list ---------------------------------------------------------- */
.chapter-item {
  display: flex; align-items: center; gap: 12px;
  background: var(--card); border-radius: 12px; box-shadow: var(--shadow);
  padding: 13px 14px; margin-bottom: 9px; width: 100%;
  border: none; text-align: left; color: var(--ink); font-family: var(--ui-font);
}
.chapter-item .ch-title { font-weight: 700; font-size: 0.95rem; }
.chapter-item .ch-sub { color: var(--ink-2); font-size: 0.78rem; }
.chapter-item .ch-mastery { margin-left: auto; flex-shrink: 0; width: 52px; }
.ring { transform: rotate(-90deg); }
.ring .bg { stroke: var(--track); }
.ring .fg { stroke: var(--pen); stroke-linecap: round; transition: stroke-dashoffset 0.4s; }
.ring-label { font-size: 0.72rem; font-weight: 700; fill: var(--ink); transform: rotate(90deg); transform-origin: center; }

/* ---- dashboard charts ------------------------------------------------------ */
.chart-block { margin-bottom: 6px; }
.chart-title { font-size: 0.85rem; font-weight: 700; color: var(--ink-2); margin-bottom: 8px; }
.mbar-row { display: flex; align-items: center; gap: 8px; margin-bottom: 7px; font-size: 0.82rem; }
.mbar-label { width: 118px; flex-shrink: 0; color: var(--ink); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.mbar-track { flex: 1; height: 14px; background: var(--track); border-radius: 4px; overflow: hidden; }
.mbar-fill { height: 100%; background: var(--pen); border-radius: 4px 0 0 4px; min-width: 2px; }
.mbar-fill.need { background: var(--cross); }
.focus-chip { font-size: 0.66rem; font-weight: 700; color: var(--cross); background: var(--cross-soft); padding: 2px 7px; border-radius: 999px; white-space: nowrap; }
.mbar-val { min-width: 38px; flex-shrink: 0; text-align: right; color: var(--ink-2); font-variant-numeric: tabular-nums; }

.dotcal { display: grid; grid-template-columns: repeat(15, 1fr); gap: 4px; }
.dotcal span { aspect-ratio: 1; border-radius: 4px; background: var(--track); }
.dotcal span.on { background: var(--hl); }
.dotcal span.today { outline: 2px solid var(--pen); }

.daily-chart { display: flex; align-items: flex-end; gap: 3px; height: 72px; }
.daily-chart .dbar { flex: 1; display: flex; flex-direction: column; justify-content: flex-end; height: 100%; border-radius: 3px 3px 0 0; overflow: hidden; background: transparent; }
.daily-chart .seg-ok { background: var(--tick); }
.daily-chart .seg-no { background: var(--track); }

.evidence-note { font-size: 0.85rem; color: var(--ink-2); padding: 8px 0 2px; border-bottom: 1px dashed var(--track); }
.evidence-note b { color: var(--ink); }

/* ---- login ------------------------------------------------------------------ */
.login-wrap { max-width: 320px; margin: 14vh auto 0; text-align: center; }
.login-wrap .logo { font-size: 2.6rem; }
.login-wrap h1 { font-size: 1.4rem; margin: 8px 0 2px; }
.login-wrap p { color: var(--ink-2); font-size: 0.9rem; margin-bottom: 20px; }
.pin-input {
  font-size: 1.8rem; letter-spacing: 0.5em; text-align: center;
  width: 100%; padding: 12px; font-family: var(--ui-font);
  border: 2px solid var(--track); border-radius: 12px;
  background: var(--card); color: var(--ink); outline: none;
}
.pin-input:focus { border-color: var(--pen); }

/* ---- bottom nav --------------------------------------------------------------- */
nav.tabbar {
  position: fixed; bottom: 0; left: 0; right: 0; z-index: 10;
  display: flex; justify-content: space-around;
  background: var(--card); box-shadow: 0 -2px 12px rgba(34, 50, 74, 0.09);
  padding: 6px 4px calc(6px + env(safe-area-inset-bottom));
}
nav.tabbar button {
  flex: 1; max-width: 110px; border: none; background: none;
  font-family: var(--ui-font); font-size: 0.68rem; font-weight: 600;
  color: var(--ink-3); padding: 4px 2px; border-radius: 10px;
}
nav.tabbar button .ico { display: block; font-size: 1.35rem; line-height: 1.3; }
nav.tabbar button.active { color: var(--pen); }

/* ---- admin ---------------------------------------------------------------------- */
.admin-field { margin-bottom: 12px; }
.admin-field label { display: block; font-size: 0.82rem; font-weight: 700; color: var(--ink-2); margin-bottom: 4px; }
.admin-field input[type="date"], .admin-field input[type="text"] {
  width: 100%; padding: 10px 12px; font-size: 1rem; font-family: var(--ui-font);
  border: 2px solid var(--track); border-radius: 10px; background: var(--card); color: var(--ink);
}
.chip-row { display: flex; flex-wrap: wrap; gap: 6px; }
.chip {
  font-size: 0.8rem; font-weight: 600; padding: 7px 11px;
  border-radius: 999px; border: 1.5px solid var(--track);
  background: var(--card); color: var(--ink-2);
}
.chip.on { background: var(--pen-soft); border-color: var(--pen); color: var(--pen); }

.doc-item { padding: 10px 0; border-bottom: 1px solid var(--track); font-size: 0.88rem; }
.doc-item .doc-label { font-weight: 700; }
.doc-item .doc-sum { color: var(--ink-2); font-size: 0.82rem; margin: 3px 0; }
.doc-find { font-size: 0.8rem; color: var(--ink-2); padding-left: 10px; }

/* toast + offline badge */
.toast {
  position: fixed; left: 50%; transform: translateX(-50%);
  bottom: calc(84px + env(safe-area-inset-bottom)); z-index: 30;
  background: var(--ink); color: var(--paper);
  padding: 10px 18px; border-radius: 999px; font-size: 0.88rem;
  box-shadow: var(--shadow); opacity: 0; transition: opacity 0.25s;
  pointer-events: none; max-width: 90vw; text-align: center;
}
.toast.show { opacity: 1; }
.offline-dot {
  display: inline-block; width: 8px; height: 8px; border-radius: 50%;
  background: var(--cross); margin-left: 6px; vertical-align: middle;
}

.empty { text-align: center; color: var(--ink-2); padding: 30px 10px; }
.empty .big { font-size: 2.4rem; margin-bottom: 6px; }

button { cursor: pointer; -webkit-tap-highlight-color: transparent; }
:focus-visible { outline: 3px solid var(--hl); outline-offset: 2px; }
@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; }
}