/* base.css — design tokens, app bar, layout primitives, forms, buttons, toasts, error pages.
   Page-specific styles live in auth.css / practice.css / history.css. No inline styles anywhere (CSP). */

:root {
  --bg: #f6f7f9;
  --surface: #ffffff;
  --text: #1b1f24;
  --muted: #5f6b7a;
  --accent: #1f6feb;
  --accent-contrast: #ffffff;
  --danger: #c93c37;
  --ok: #1f8a4c;
  --bubble-tutor: #e9eef7;
  --bubble-learner: #dff3e6;
  --mark: #fff1a8;
  --border: #d9dee6;
  --radius: 14px;
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 16px;
  --space-4: 24px;
  --font: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  --appbar-h: 56px;
  --bar-h: 88px;
  --shadow: 0 1px 2px rgba(16, 20, 24, 0.08), 0 4px 16px rgba(16, 20, 24, 0.06);
  --focus: 0 0 0 3px color-mix(in srgb, var(--accent) 40%, transparent);
  color-scheme: light;
}

[data-theme="dark"] {
  --bg: #101418;
  --surface: #181d23;
  --text: #e6e9ee;
  --muted: #9aa5b4;
  --accent: #6ea8ff;
  --accent-contrast: #0b1220;
  --danger: #ff6b66;
  --ok: #4cc27a;
  --bubble-tutor: #1f2a3a;
  --bubble-learner: #1b3326;
  --mark: #5d4d00;
  --border: #2a323c;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.5), 0 4px 16px rgba(0, 0, 0, 0.35);
  color-scheme: dark;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #101418;
    --surface: #181d23;
    --text: #e6e9ee;
    --muted: #9aa5b4;
    --accent: #6ea8ff;
    --accent-contrast: #0b1220;
    --danger: #ff6b66;
    --ok: #4cc27a;
    --bubble-tutor: #1f2a3a;
    --bubble-learner: #1b3326;
    --mark: #5d4d00;
    --border: #2a323c;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.5), 0 4px 16px rgba(0, 0, 0, 0.35);
    color-scheme: dark;
  }
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
  height: 100%;
}

body {
  margin: 0;
  min-height: 100vh;
  min-height: 100dvh;
  display: grid;
  grid-template-rows: auto 1fr auto;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

h1,
h2,
h3 {
  line-height: 1.2;
  margin: 0 0 var(--space-3);
}

h1 { font-size: 1.6rem; }
h2 { font-size: 1.3rem; }
h3 { font-size: 1.1rem; }

p { margin: 0 0 var(--space-3); }

a {
  color: var(--accent);
  text-decoration-thickness: 1px;
  text-underline-offset: 2px;
}

code,
pre {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.9em;
}

pre {
  overflow: auto;
  padding: var(--space-3);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
}

.muted { color: var(--muted); }

[hidden] { display: none !important; }

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

:focus-visible {
  outline: none;
  box-shadow: var(--focus);
  border-radius: 6px;
}

.skip-link {
  position: absolute;
  left: var(--space-3);
  top: -100px;
  z-index: 100;
  padding: var(--space-2) var(--space-3);
  background: var(--surface);
  border-radius: var(--radius);
}

.skip-link:focus { top: var(--space-2); }

/* ---- Icons (inline SVG sprite) ---- */
.icon {
  width: 1.25em;
  height: 1.25em;
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
  vertical-align: -0.3em;
  flex: none;
}

/* ---- App bar ---- */
.appbar {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  gap: var(--space-2);
  min-height: var(--appbar-h);
  padding: 0 var(--space-3);
  padding-top: env(safe-area-inset-top);
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}

.appbar__logo {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text);
  text-decoration: none;
  min-height: 44px;
}

.appbar__toggle {
  margin-left: auto;
}

.appbar__toggle .icon { transition: transform 0.2s; }
.appbar__toggle[aria-expanded="true"] .icon { transform: rotate(180deg); }

.appbar__nav {
  display: none;
  position: absolute;
  left: 0;
  right: 0;
  top: 100%;
  flex-direction: column;
  gap: var(--space-2);
  padding: var(--space-3);
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow);
}

.appbar__nav.is-open { display: flex; }

.appbar__link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  min-height: 44px;
  padding: 0 var(--space-3);
  border-radius: var(--radius);
  color: var(--text);
  text-decoration: none;
  font-weight: 500;
}

.appbar__link:hover { background: var(--bubble-tutor); }
.appbar__link.is-active { color: var(--accent); background: color-mix(in srgb, var(--accent) 12%, transparent); }

.appbar__form {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  margin: 0;
}

@media (min-width: 640px) {
  /* `.appbar` prefix: the generic `.btn { display: inline-flex }` rule is declared later with the same specificity and would otherwise win. */
  .appbar .appbar__toggle { display: none; }
  .appbar__nav {
    display: flex;
    position: static;
    flex-direction: row;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--space-1);
    margin-left: auto;
    padding: 0;
    border: 0;
    box-shadow: none;
    background: transparent;
  }
  .appbar__link span { display: none; }
  .appbar__link { padding: 0 var(--space-2); }
}

@media (min-width: 1024px) {
  .appbar__link span { display: inline; }
  .appbar__link { padding: 0 var(--space-3); }
}

/* ---- Main / footer ---- */
.main {
  width: 100%;
  max-width: 1100px;
  margin: 0 auto;
  padding: var(--space-3);
  padding-left: max(var(--space-3), env(safe-area-inset-left));
  padding-right: max(var(--space-3), env(safe-area-inset-right));
}

@media (min-width: 640px) {
  .main { padding: var(--space-4); }
}

.footer {
  display: none;
  padding: var(--space-3) var(--space-4);
  color: var(--muted);
  font-size: 0.85rem;
  text-align: center;
}

@media (min-width: 640px) {
  .footer { display: block; }
}

/* ---- Cards ---- */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-3);
  box-shadow: var(--shadow);
}

/* ---- Buttons ---- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  min-height: 44px;
  min-width: 44px;
  padding: 0 var(--space-3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text);
  font: inherit;
  font-weight: 500;
  cursor: pointer;
  text-decoration: none;
  touch-action: manipulation;
}

.btn:hover { background: var(--bubble-tutor); }
.btn:disabled,
.btn[aria-disabled="true"] { opacity: 0.55; cursor: not-allowed; }

.btn--primary {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--accent-contrast);
}

.btn--primary:hover { filter: brightness(1.08); background: var(--accent); }

.btn--danger { color: var(--danger); border-color: color-mix(in srgb, var(--danger) 50%, var(--border)); }
.btn--ghost { border-color: transparent; background: transparent; }
.btn--icon { padding: 0; width: 44px; }
.btn--chip { min-height: 36px; min-width: 36px; padding: 0 var(--space-2); border-radius: 999px; font-size: 0.9rem; }
.btn--chip.btn--icon { width: 36px; }
.btn--chip.is-active { background: var(--accent); border-color: var(--accent); color: var(--accent-contrast); }
/* SPEC §11.1: touch targets >= 44 px — chips stay compact (36 px) only for mouse pointers. */
@media (pointer: coarse) {
  .btn--chip { min-height: 44px; min-width: 44px; }
  .btn--chip.btn--icon { width: 44px; }
}
.btn--round { border-radius: 50%; width: 64px; height: 64px; }

/* ---- Forms ---- */
.field { display: flex; flex-direction: column; gap: var(--space-1); margin-bottom: var(--space-3); }
.field label { font-weight: 500; }
.field .hint { color: var(--muted); font-size: 0.9rem; }
.field .error { color: var(--danger); font-size: 0.9rem; }

input:not([type="checkbox"]):not([type="radio"]):not([type="range"]),
select,
textarea {
  width: 100%;
  min-height: 44px;
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--surface);
  color: var(--text);
  font: inherit;
}

textarea { min-height: 96px; resize: vertical; }

input[aria-invalid="true"],
select[aria-invalid="true"],
textarea[aria-invalid="true"] { border-color: var(--danger); }

/* ---- Flash / toasts ---- */
.flash {
  margin-bottom: var(--space-3);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--surface);
}

.flash--success { border-color: var(--ok); }
.flash--error { border-color: var(--danger); }

.toasts {
  position: fixed;
  left: 50%;
  bottom: calc(var(--space-3) + env(safe-area-inset-bottom));
  transform: translateX(-50%);
  z-index: 200;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  width: min(92vw, 420px);
  pointer-events: none;
}

.toast {
  pointer-events: auto;
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius);
  background: var(--text);
  color: var(--bg);
  box-shadow: var(--shadow);
  animation: toast-in 0.2s ease-out;
}

.toast--error { background: var(--danger); color: #fff; }
.toast--success { background: var(--ok); color: #fff; }

@keyframes toast-in {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: none; }
}

/* ---- Error pages ---- */
.error-page {
  max-width: 640px;
  margin: 10vh auto 0;
  text-align: center;
}

.error-page__status {
  font-size: 4rem;
  font-weight: 800;
  color: var(--muted);
  margin: 0;
  line-height: 1;
}

.error-page__debug { text-align: left; margin: var(--space-3) 0; }
.error-page__debug pre { white-space: pre-wrap; overflow-wrap: anywhere; }

/* ---- Utilities ---- */
.stack > * + * { margin-top: var(--space-3); }
.row { display: flex; flex-wrap: wrap; gap: var(--space-2); align-items: center; }
.grow { flex: 1 1 auto; }
.text-is { font-weight: 500; overflow-wrap: anywhere; }
mark { background: var(--mark); color: inherit; border-radius: 3px; padding: 0 2px; }

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
}