/* ---------------------------------------------------------------
   Mathclair — voice math tutor
   Identity: calm "graph-paper / ink" theme.
   Ink indigo for trust + focus, one warm coral accent reserved
   only for the live "listening" state. Answers land on a faint
   grid card, like a worked solution on graph paper.
----------------------------------------------------------------*/
:root {
  --paper:      #F7F8FB;
  --paper-2:    #FFFFFF;
  --grid:       #E7EBF5;
  --ink:        #1B2233;
  --ink-soft:   #5B6478;
  --indigo:     #3D52D5;
  --indigo-050: #EEF1FE;
  --indigo-200: #C3CBF6;
  --coral:      #E8663D;
  --line:       #E3E7F1;
  --radius:     16px;
  --shadow:     0 1px 2px rgba(27,34,51,.04), 0 8px 24px rgba(27,34,51,.06);
  --font-body:  'Inter', system-ui, -apple-system, sans-serif;
  --font-disp:  'Space Grotesk', var(--font-body);
}

* { box-sizing: border-box; }
html, body { height: 100%; margin: 0; }

body {
  font-family: var(--font-body);
  color: var(--ink);
  background: var(--paper);
  /* faint graph-paper grid */
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 26px 26px;
  -webkit-font-smoothing: antialiased;
}

.app {
  max-width: 640px;
  margin: 0 auto;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  padding: env(safe-area-inset-top) 0 env(safe-area-inset-bottom);
}

/* ---------- top bar ---------- */
.topbar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 16px 20px;
  position: sticky; top: 0; z-index: 5;
  background: color-mix(in srgb, var(--paper) 86%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 12px; }
.brand-mark {
  font-family: var(--font-disp);
  font-size: 26px; line-height: 1;
  width: 44px; height: 44px; border-radius: 12px;
  display: grid; place-items: center;
  background: var(--indigo); color: #fff;
  box-shadow: var(--shadow);
}
.brand-text h1 { font-family: var(--font-disp); font-size: 19px; font-weight: 700; margin: 0; letter-spacing: -0.01em; }
.brand-text p  { font-size: 12px; color: var(--ink-soft); margin: 2px 0 0; }

.icon-btn {
  border: 1px solid var(--line); background: var(--paper-2);
  width: 44px; height: 44px; border-radius: 12px; cursor: pointer;
  font-size: 18px; display: grid; place-items: center;
}
.icon-btn .speaker-off { display: none; }
.icon-btn[aria-pressed="false"] .speaker-on { display: none; }
.icon-btn[aria-pressed="false"] .speaker-off { display: inline; }

/* ---------- chat ---------- */
.chat {
  flex: 1;
  padding: 20px;
  display: flex; flex-direction: column; gap: 14px;
  overflow-y: auto;
}
.msg { max-width: 84%; padding: 12px 15px; border-radius: var(--radius); line-height: 1.5; font-size: 15.5px; }
.msg.user {
  align-self: flex-end;
  background: var(--indigo-050);
  border: 1px solid var(--indigo-200);
  color: var(--ink);
  border-bottom-right-radius: 5px;
}
.msg.tutor {
  align-self: flex-start;
  background: var(--paper-2);
  border: 1px solid var(--line);
  border-bottom-left-radius: 5px;
  box-shadow: var(--shadow);
  /* worked-solution grid inside tutor answers */
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 22px 22px;
  background-position: -1px -1px;
}
.msg .src { display:block; margin-top:6px; font-size:11px; color:var(--ink-soft); letter-spacing:.02em; }
.msg.tutor .answer { font-family: var(--font-disp); font-weight: 600; }

/* ---------- inline math notation (rendered via KaTeX) ---------- */
.msg .katex { font-size: 1.05em; }
.msg .katex-html { white-space: normal; }

.msg.empty {
  align-self: center; text-align: center; color: var(--ink-soft);
  background: transparent; border: none; box-shadow: none; max-width: 100%;
  margin-top: 8vh;
}
.msg.empty h2 { font-family: var(--font-disp); font-weight:600; color: var(--ink); margin: 0 0 6px; }
.msg.empty p { margin: 0; font-size: 14px; }

/* typing indicator */
.typing { display:inline-flex; gap:5px; align-items:center; }
.typing span { width:7px; height:7px; border-radius:50%; background:var(--indigo-200); animation: bob 1s infinite; }
.typing span:nth-child(2){ animation-delay:.15s; } .typing span:nth-child(3){ animation-delay:.3s; }
@keyframes bob { 0%,60%,100%{transform:translateY(0);opacity:.5} 30%{transform:translateY(-4px);opacity:1} }

/* ---------- status ---------- */
.status-bar { min-height: 20px; padding: 0 20px 4px; font-size: 13px; color: var(--coral); text-align: center; }

/* ---------- composer ---------- */
.composer {
  display: flex; gap: 10px; align-items: center;
  padding: 12px 16px calc(12px + env(safe-area-inset-bottom));
  border-top: 1px solid var(--line);
  background: var(--paper-2);
}
.composer-form { flex: 1; display: flex; gap: 8px; }
.text-input {
  flex: 1; border: 1px solid var(--line); border-radius: 999px;
  padding: 13px 18px; font-size: 15px; font-family: var(--font-body);
  background: var(--paper); color: var(--ink); outline: none;
}
.text-input:focus { border-color: var(--indigo); box-shadow: 0 0 0 3px var(--indigo-050); }
.send-btn {
  border: none; background: var(--indigo); color: #fff;
  width: 46px; height: 46px; border-radius: 50%; font-size: 20px; cursor: pointer;
  flex-shrink: 0;
}
.send-btn:disabled { opacity: .45; cursor: default; }

/* mic — the signature element */
.mic-btn {
  position: relative; flex-shrink: 0;
  width: 52px; height: 52px; border-radius: 50%;
  border: 1px solid var(--line); background: var(--paper-2);
  cursor: pointer; font-size: 22px; display: grid; place-items: center;
  transition: transform .12s ease;
}
.mic-btn:active { transform: scale(.94); }
.mic-btn.hidden { display: none; }
.mic-ring {
  position: absolute; inset: -4px; border-radius: 50%;
  border: 2px solid var(--coral); opacity: 0; pointer-events: none;
}
.mic-btn.listening { background: color-mix(in srgb, var(--coral) 12%, #fff); border-color: var(--coral); }
@media (prefers-reduced-motion: no-preference) {
  .mic-btn.listening .mic-ring { animation: pulse 1.4s ease-out infinite; }
}
@keyframes pulse { 0%{opacity:.9; transform:scale(.9)} 100%{opacity:0; transform:scale(1.5)} }

/* ---------- dark mode ---------- */
@media (prefers-color-scheme: dark) {
  :root {
    --paper:#10131F; --paper-2:#171B2A; --grid:#20263A; --ink:#E7EAF3;
    --ink-soft:#9AA3BD; --indigo:#6C7CF0; --indigo-050:#20263F; --indigo-200:#3A447A;
    --line:#262C40; --coral:#F2865E; --shadow:0 8px 24px rgba(0,0,0,.35);
  }
}