/* =============================================================================
   f(x) · styles — im Geiste von LoveFrom: klassische Serife, warmes Papier,
   nahezu monochrom, sehr still. Hell & Dunkel.
   ============================================================================= */
:root {
  --serif: "Hoefler Text", "Iowan Old Style", "Palatino Linotype",
           "Book Antiqua", Palatino, Georgia, Cambria, "Times New Roman", serif;

  --bg: #F1F1F0;             /* neutrales Papier, kein Gelbstich */
  --panel: rgba(250, 250, 249, 0.86);
  --panel-solid: #FBFBFA;
  --panel-border: rgba(28, 28, 32, 0.12);
  --shadow: 0 10px 44px rgba(18, 18, 22, 0.12), 0 1px 2px rgba(18, 18, 22, 0.06);
  --shadow-soft: 0 6px 26px rgba(18, 18, 22, 0.10);
  --ink: #242427;
  --text: #242427;
  --text-2: #646469;
  --text-3: #97979D;
  --hair: rgba(28, 28, 32, 0.10);
  --fill: rgba(20, 20, 24, 0.045);
  --fill-hover: rgba(20, 20, 24, 0.075);
  --accent: #6E88A6;         /* Schiefer, sehr sparsam */
  --danger: #A24A3A;
  --radius-lg: 18px;
  --radius: 12px;
  --radius-sm: 9px;
  --ease: cubic-bezier(0.32, 0.72, 0, 1);
}
:root[data-theme="dark"] {
  --bg: #161617;             /* neutrale Kohle, kein Braunstich */
  --panel: rgba(32, 32, 34, 0.82);
  --panel-solid: #202022;
  --panel-border: rgba(236, 236, 240, 0.13);
  --shadow: 0 10px 44px rgba(0, 0, 0, 0.5), 0 1px 2px rgba(0, 0, 0, 0.4);
  --shadow-soft: 0 6px 26px rgba(0, 0, 0, 0.42);
  --ink: #ECECEE;
  --text: #ECECEE;
  --text-2: #9A9AA0;
  --text-3: #66666C;
  --hair: rgba(236, 236, 240, 0.11);
  --fill: rgba(236, 236, 240, 0.06);
  --fill-hover: rgba(236, 236, 240, 0.11);
  --accent: #7FA0B8;
  --danger: #C56E5C;
}
@media (prefers-color-scheme: dark) {
  :root[data-theme="auto"] {
    --bg: #161617;
    --panel: rgba(32, 32, 34, 0.82);
    --panel-solid: #202022;
    --panel-border: rgba(236, 236, 240, 0.13);
    --shadow: 0 10px 44px rgba(0, 0, 0, 0.5), 0 1px 2px rgba(0, 0, 0, 0.4);
    --shadow-soft: 0 6px 26px rgba(0, 0, 0, 0.42);
    --ink: #ECECEE;
    --text: #ECECEE;
    --text-2: #9A9AA0;
    --text-3: #66666C;
    --hair: rgba(236, 236, 240, 0.11);
    --fill: rgba(236, 236, 240, 0.06);
    --fill-hover: rgba(236, 236, 240, 0.11);
    --accent: #7FA0B8;
    --danger: #C56E5C;
  }
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html, body { height: 100%; overflow: hidden; }
button, a, [role="button"] {
  -webkit-tap-highlight-color: transparent;
  -webkit-touch-callout: none;
}
button:focus, button:focus-visible { outline: none; }
body {
  font-family: var(--serif);
  font-feature-settings: "onum" 1, "liga" 1, "kern" 1;
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  user-select: none;
  -webkit-user-select: none;
}

#app { position: fixed; inset: 0; }
canvas {
  position: absolute; inset: 0; width: 100%; height: 100%; display: block;
  /* Ohne dies deutet der Browser Wischen als Scrollen/Zoomen, bricht den
     laufenden Zeiger mit `pointercancel` ab — und man müsste absetzen. */
  touch-action: none;
  -webkit-touch-callout: none;
  -webkit-tap-highlight-color: transparent;
}
#base { z-index: 1; }
#overlay { z-index: 2; pointer-events: none; }
#base { cursor: crosshair; }
#base.grabbing { cursor: grabbing; }
#base.reading { cursor: crosshair; }

/* ---------------------------------------------------------------------------
   Panel (Funktionen) — wie eine Karte aus feinem Papier
   --------------------------------------------------------------------------- */
.panel {
  position: absolute;
  top: 20px; left: 20px;
  width: 300px;
  max-height: calc(100vh - 40px);
  z-index: 5;
  background: var(--panel);
  -webkit-backdrop-filter: saturate(140%) blur(16px);
  backdrop-filter: saturate(140%) blur(16px);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
  padding: 14px;
  display: flex;
  flex-direction: column;
  transition: transform 0.5s var(--ease), opacity 0.35s var(--ease);
  overflow: hidden;
}
.panel.collapsed { transform: translateX(-120%); opacity: 0; pointer-events: none; }

.panel-head {
  display: flex; align-items: center; justify-content: space-between;
  padding: 2px 4px 14px 6px;
}
.wordmark {
  font-family: var(--serif);
  font-style: italic;
  font-size: 25px; font-weight: 500; letter-spacing: 0.01em;
  color: var(--ink);
}
.wordmark .paren { color: var(--text-3); font-style: italic; }

.panel-scroll {
  flex: 1 1 auto; min-height: 0;
  display: flex; flex-direction: column;
  overflow-y: auto;
}
.panel-scroll::-webkit-scrollbar { width: 0; }
.fn-list { display: flex; flex-direction: column; }

/* Gruppe pro Funktion: Kopfzeile + aufklappbare Objektliste */
.fn-group + .fn-group { border-top: 1px solid var(--hair); }

.fn-row {
  display: flex; align-items: center; gap: 9px;
  border-radius: var(--radius);
  padding: 10px 8px 10px 2px;
  transition: background 0.2s var(--ease);
  position: relative;
}
.fn-row:hover { background: var(--fill); }
.fn-row.invalid .fn-label { color: var(--danger); }

.fn-chevron {
  width: 22px; height: 22px; flex-shrink: 0;
  border: none; background: transparent; padding: 0;
  display: grid; place-items: center;
  color: var(--text-3); cursor: pointer;
  transition: transform 0.4s var(--ease), opacity 0.25s var(--ease), color 0.2s;
}
.fn-chevron:hover { color: var(--ink); }
.fn-group.open > .fn-row .fn-chevron { transform: rotate(90deg); }
.fn-chevron.none { opacity: 0; pointer-events: none; }

.fn-objects {
  display: grid; grid-template-rows: 0fr;
  transition: grid-template-rows 0.45s var(--ease), opacity 0.35s var(--ease);
  opacity: 0;
}
.fn-group.open .fn-objects { grid-template-rows: 1fr; opacity: 1; }
.fn-objects > div { overflow: hidden; }
.fn-objects .obj-inner { padding: 0 4px 10px 30px; }

.obj-label {
  font-style: italic; font-size: 12px; color: var(--text-3);
  padding: 7px 10px 3px 8px;
}

.fn-dot {
  width: 12px; height: 12px; border-radius: 50%;
  flex-shrink: 0; cursor: pointer;
  transition: transform 0.18s var(--ease);
}
.fn-dot:hover { transform: scale(1.18); }
.fn-dot.off { background: transparent !important; box-shadow: inset 0 0 0 1.5px var(--text-3); }

.fn-body { flex: 1; min-width: 0; display: flex; align-items: baseline; gap: 6px; }
.fn-label {
  font-family: var(--serif); font-style: italic;
  font-size: 16px; color: var(--text-2); flex-shrink: 0;
}

/* Term-Feld: gesetzte Anzeige (fn-pretty) und Eingabe (fn-input) teilen sich den Platz. */
.fn-field { flex: 1; min-width: 0; }

.fn-input {
  width: 100%; min-width: 0;
  border: none; outline: none; background: transparent;
  font-family: var(--serif);
  font-size: 16px; color: var(--text);
  letter-spacing: 0.01em;
  font-feature-settings: "onum" 1;
  caret-color: var(--accent);
  display: none;
}
.fn-input::placeholder { color: var(--text-3); font-style: italic; }

/* Gesetzter, nur lesbarer Term — echte Hochzahlen, gut zu markieren & kopieren. */
.fn-pretty {
  display: none;
  min-width: 0; cursor: text;
  font-family: var(--serif);
  font-size: 16px; color: var(--text);
  letter-spacing: 0.01em;
  font-feature-settings: "onum" 1;
  line-height: 1.35;
  white-space: nowrap; overflow-x: auto; overflow-y: hidden;
  scrollbar-width: none;
  border-radius: 5px;
  outline: none;
}
.fn-pretty::-webkit-scrollbar { height: 0; }
.fn-pretty::selection { background: color-mix(in srgb, var(--accent, #b8860b) 26%, transparent); }
.fn-pretty:focus-visible { box-shadow: 0 0 0 2px color-mix(in srgb, var(--text-3) 55%, transparent); }

/* ---------------------------------------------------------------------------
   Zweidimensional gesetzte Terme (Schulbuch- / GeoGebra-Stil).
   Erzeugt von FX.termToRichHtml. Erscheint überall, wo ein Funktionsterm steht
   (gesetzter Term, Ableitungen, Spiegelungen). Maße in em, damit es sich der
   jeweiligen Schriftgröße (Panel-Term wie Objektzeile) anpasst.
   --------------------------------------------------------------------------- */
sup { font-size: 0.72em; line-height: 0; }

/* Bruch — Zähler über Nenner, dünner Bruchstrich. */
.fx-frac {
  display: inline-flex; flex-direction: column;
  vertical-align: middle; text-align: center;
  margin: 0 0.16em;
}
.fx-num { padding: 0 0.34em 0.08em; border-bottom: 1.1px solid currentColor; }
.fx-den { padding: 0.06em 0.34em 0; }
.fx-num, .fx-den { display: block; line-height: 1.18; }

/* Wurzel — Radikalzeichen + Radikand mit Überstrich (Vinkulum). */
.fx-root { display: inline-flex; align-items: stretch; white-space: nowrap; }
.fx-radsign {
  display: inline-flex; align-items: flex-end;
  font-size: 1.02em; line-height: 1;
  transform: scaleY(1.12); transform-origin: bottom;
  margin-right: 0.02em;
}
.fx-radicand {
  border-top: 1.1px solid currentColor;
  padding: 0.12em 0.24em 0 0.14em;
}
.fx-rootidx {
  font-size: 0.62em; align-self: flex-start;
  margin-right: -0.32em; transform: translateY(-0.15em);
}

/* Betrag — senkrechte Balken, die mit dem Inhalt mitwachsen. */
.fx-abs {
  display: inline-flex;
  border-left: 1.1px solid currentColor; border-right: 1.1px solid currentColor;
  padding: 0 0.24em; margin: 0 0.1em;
}

/* Operatorwort (mod) tritt leicht zurück. */
.fx-op { font-style: italic; color: var(--text-2); padding: 0 0.1em; }

/* Sichtbarkeit: gesetzter Term im Ruhezustand, Eingabefeld beim Bearbeiten/leer. */
.fn-field.has-pretty:not(.editing) .fn-pretty { display: block; }
.fn-field.editing .fn-input,
.fn-field:not(.has-pretty) .fn-input { display: block; }

.fn-copy, .fn-remove {
  opacity: 0; width: 20px; height: 20px; flex-shrink: 0;
  border: none; background: transparent; color: var(--text-3);
  cursor: pointer; border-radius: 50%; display: grid; place-items: center;
  transition: opacity 0.18s, color 0.18s;
}
.fn-copy { margin-left: 2px; }
.fn-row:hover .fn-copy.avail, .fn-row:hover .fn-remove { opacity: 1; }
.fn-copy:hover { color: var(--ink); }
.fn-remove:hover { color: var(--danger); }

.fn-error {
  font-family: var(--serif); font-style: italic;
  font-size: 13px; color: var(--danger);
  padding: 2px 12px 4px; line-height: 1.4;
}

.add-fn {
  margin-top: 8px; align-self: flex-start;
  display: flex; align-items: center; gap: 7px;
  border: none; background: transparent;
  color: var(--text-2); font-family: var(--serif); font-style: italic;
  font-size: 15px;
  cursor: pointer; padding: 8px 8px; border-radius: var(--radius);
  transition: color 0.2s var(--ease);
}
.add-fn svg { opacity: 0.7; }
.add-fn:hover { color: var(--ink); }

/* Objektzeilen innerhalb einer Gruppe */
.measure {
  display: flex; align-items: center; gap: 10px;
  padding: 6px 8px; border-radius: var(--radius-sm);
  font-size: 13.5px;
  transition: background 0.18s;
}
.measure:hover { background: var(--fill); cursor: pointer; }
.measure.sel { background: var(--fill); }
.measure .m-swatch {
  width: 8px; height: 8px; border-radius: 50%; flex-shrink: 0;
  cursor: pointer;
  transition: transform 0.18s var(--ease);
}
.measure .m-swatch:hover { transform: scale(1.35); }
.measure .m-swatch.off { background: transparent !important; box-shadow: inset 0 0 0 1.5px var(--text-3); }
.measure.hidden .m-text { opacity: 0.45; }
.measure .m-text { flex: 1; min-width: 0; color: var(--text); }
.measure .m-text b { font-weight: 600; font-feature-settings: "onum" 1; }
.measure .m-text .m-kind {
  color: var(--text-2); font-size: 12.5px; font-style: italic; display: block; margin-top: 1px;
}
.measure .m-copy {
  opacity: 0; width: 18px; height: 18px; flex-shrink: 0;
  border: none; background: transparent; color: var(--text-3);
  cursor: pointer; border-radius: 50%; display: grid; place-items: center;
  transition: opacity 0.18s, color 0.18s;
}
.measure:hover .m-copy { opacity: 1; }
.measure .m-copy:hover { color: var(--ink); }
.measure .m-remove {
  border: none; background: transparent; color: var(--text-3);
  cursor: pointer; font-size: 17px; line-height: 1; padding: 2px;
  transition: color 0.15s;
}
.measure .m-remove:hover { color: var(--danger); }

/* ---------------------------------------------------------------------------
   Bedienelemente — zurückhaltend, typografisch
   --------------------------------------------------------------------------- */
.icon-btn {
  width: 40px; height: 40px;
  display: grid; place-items: center;
  margin: 2px;
  border: none;
  background: transparent;
  color: var(--text-2);
  border-radius: 50%;
  cursor: pointer;
  transition: color 0.2s var(--ease), background 0.2s var(--ease), transform 0.15s var(--ease);

  /* BUTTON PANEL */
  background: var(--panel);
  -webkit-backdrop-filter: blur(16px); backdrop-filter: blur(16px);
  box-shadow: var(--shadow-soft);
  /*  */
}
.icon-btn.ghost { width: 30px; height: 30px; }
/*.icon-btn:hover { color: var(--ink); background: var(--fill); }*/
.icon-btn:active { transform: scale(0.92); }
.icon-btn.active { color: var(--ink); }

.top-right {
  position: absolute; top: 22px; right: 22px; z-index: 5;
  display: flex; gap: 6px;
}

.panel-reveal {
  position: absolute; top: 22px; left: 22px; z-index: 5;
  opacity: 0; transform: translateX(-8px); pointer-events: none;
  transition: opacity 0.35s var(--ease), transform 0.35s var(--ease);
  background: var(--panel);
  -webkit-backdrop-filter: blur(16px); backdrop-filter: blur(16px);
  box-shadow: var(--shadow-soft);
}
.panel-reveal.show { opacity: 1; transform: none; pointer-events: auto; }

.dock {
  position: absolute; bottom: 24px; left: 50%; transform: translateX(-50%);
  z-index: 5;
  display: flex; align-items: stretch; gap: 0; padding: 7px 10px 8px;
  background: var(--panel);
  -webkit-backdrop-filter: saturate(140%) blur(16px);
  backdrop-filter: saturate(140%) blur(16px);
  border: 1px solid var(--panel-border);
  border-radius: 16px;
  box-shadow: var(--shadow);
}
/* Jede Absicht ist eine kleine Spalte: leise Überschrift + ihre Werkzeuge */
.dock-group {
  display: flex; flex-direction: column; align-items: center;
  gap: 3px; padding: 0 6px;
}
.dock-cap {
  font-family: var(--serif); font-style: italic;
  font-size: 11px; letter-spacing: 0.03em; line-height: 1;
  color: var(--text-3);
}
.dock-tools { display: flex; gap: 2px; }
.seg-pill { display: none; }   /* nur auf Smartphones aktiviert, siehe unten */
.dock button {
  position: relative;
  border: none; background: transparent;
  color: var(--text-2);
  font-family: var(--serif); font-size: 15.5px; letter-spacing: 0.01em;
  padding: 6px 14px 8px; border-radius: 9px;
  cursor: pointer;
  transition: color 0.22s var(--ease);
}
.dock button:hover { color: var(--ink); }         /* text-forward, keine Pille */
.dock button.active { color: var(--ink); }
.dock button.active::after {
  content: ''; position: absolute; left: 14px; right: 14px; bottom: 3px;
  height: 1.5px; background: var(--ink); border-radius: 1px;
}
.dock-sep {
  width: 1px; align-self: stretch; flex-shrink: 0;
  margin: 2px 3px; background: var(--hair);
}

@media (max-width: 760px) {
  .dock { padding: 6px 6px 7px; }
  .dock-group { padding: 0 3px; }
  .dock button { padding: 6px 9px 8px; font-size: 13.5px; }
  .dock button.active::after { left: 9px; right: 9px; }
  .dock-cap { font-size: 10px; }
  .dock-sep { margin: 2px 2px; }
}

/* Berührung statt Maus: Kopieren/Entfernen können nicht erst beim Hover
   erscheinen, sonst bleiben sie auf Touch-Geräten unerreichbar. */
@media (hover: none) and (pointer: coarse) {
  .fn-copy.avail, .fn-remove, .measure .m-copy { opacity: 1; }
}

/* ---------------------------------------------------------------------------
   Smartphone — schmale Bildschirme (Hochformat wie Querformat).
   Kopfzeile (Panel) und Steuerung (oben rechts) stehen übereinander statt
   nebeneinander, das Dock wird bei Bedarf horizontal wischbar statt zu quetschen.
   --------------------------------------------------------------------------- */
@media (max-width: 640px) {
  .top-right { top: 14px; right: 14px; }
  .panel, .panel-reveal { top: 66px; left: 14px; }
  .panel { right: 14px; width: auto; max-height: calc(100vh - 66px - 14px); }
  .panel-reveal.show { top: 14px; }

  .dock {
    max-width: calc(100vw - 20px);
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
    justify-content: flex-start;
  }
  .dock::-webkit-scrollbar { display: none; }
  .dock-group { flex-shrink: 0; }
}

/* Nur auf echten Smartphones (schmal + grobes Zeigegerät): die Auswahl folgt
   dem iOS-Kamera-Wähler — eine Kapsel, die beim Wischen über die GESAMTE
   Leiste (gruppenübergreifend) gleitet, statt der textbetonten
   Unterstreichung für Maus/Trackpad. Gewählt wird ausschließlich per Wischen:
   ein bloßes Antippen bleibt vollkommen wirkungslos und zeigt auch keinerlei
   Rückmeldung. Die Trennlinien zwischen den Absichten (Ansicht · Funktion ·
   Messen) bleiben rein optisch. */
@media (max-width: 640px) and (pointer: coarse) {
  /* Horizontales Scrollen gehört uns (Wisch-Wähler), nicht dem Browser.
     Kein grauer Tap-Blitz, keine Textauswahl beim Ziehen. */
  .dock {
    touch-action: pan-y;
    -webkit-tap-highlight-color: transparent;
    -webkit-user-select: none; user-select: none;
  }
  .seg-pill {
    display: block;
    position: absolute; left: 0; top: 0;
    width: 0; height: 0; border-radius: 8px;
    background: var(--panel-solid);
    box-shadow: 0 1px 3px rgba(18, 18, 22, 0.16), 0 0 0 0.5px var(--panel-border);
    /* Kurz gehalten: die Kapsel folgt einem direkt geführten Finger — eine
       längere Kurve würde ihm sichtbar hinterherhinken. */
    transition: transform 0.16s var(--ease), width 0.16s var(--ease), height 0.16s var(--ease), opacity 0.18s var(--ease);
    opacity: 0; pointer-events: none; z-index: 0;
  }
  .seg-pill.seg-ready { opacity: 1; }
  /* Die Buttons sind reine Beschriftung: der Wisch wird vom Dock behandelt,
     die Knöpfe selbst nehmen keine Zeigereignisse an. Damit gibt es beim
     Antippen weder Hover-/Aktiv-Farbe noch Hinterlegung noch Fokusring —
     einzig „.active“ (die Auswahl) färbt den Text. */
  .dock button {
    position: relative; z-index: 1;
    pointer-events: none;
    cursor: default;
    -webkit-tap-highlight-color: transparent;
  }
  .dock button:hover,
  .dock button:active,
  .dock button:focus,
  .dock button:focus-visible {
    color: var(--text-2);            /* unverändert — nur .active hebt sich ab */
    background: transparent;
    outline: none; box-shadow: none;
  }
  .dock button.active,
  .dock button.active:hover,
  .dock button.active:active { color: var(--ink); }
  .dock button.active::after { display: none; }   /* Kapsel ersetzt die Linie */
}

/* ---------------------------------------------------------------------------
   Objekt-Eingabe (Punkt / Tangente) — Pille über dem Dock
   --------------------------------------------------------------------------- */
.tool-input {
  position: absolute; bottom: 112px; left: 50%;
  transform: translateX(-50%) translateY(8px);
  z-index: 5;
  display: flex; align-items: center; gap: 8px;
  padding: 6px 6px 6px 14px;
  background: var(--panel);
  -webkit-backdrop-filter: saturate(140%) blur(16px);
  backdrop-filter: saturate(140%) blur(16px);
  border: 1px solid var(--panel-border);
  border-radius: 12px;
  box-shadow: var(--shadow-soft);
  opacity: 0; pointer-events: none;
  transition: opacity 0.3s var(--ease), transform 0.3s var(--ease), bottom 0.3s var(--ease);
}
.tool-input.show { opacity: 1; pointer-events: auto; transform: translateX(-50%) translateY(0); }
body.kb-open .tool-input { bottom: calc(var(--kb-h, 0px) + 12px); }
.tool-input .ti-label {
  font-family: var(--serif); font-style: italic;
  font-size: 15px; color: var(--text-2); flex-shrink: 0;
}
.tool-input input {
  width: 168px; border: none; outline: none; background: transparent;
  font-family: var(--serif); font-size: 15.5px; color: var(--text);
  letter-spacing: 0.01em; font-feature-settings: "onum" 1;
  caret-color: var(--accent);
}
.tool-input input::placeholder { color: var(--text-3); font-style: italic; }
.tool-input.invalid input, .tool-input.invalid input::placeholder { color: var(--danger); }
.tool-input .ti-add {
  width: 30px; height: 30px; flex-shrink: 0;
  border: none; background: var(--fill); color: var(--text-2);
  border-radius: 8px; display: grid; place-items: center; cursor: pointer;
  transition: color 0.2s var(--ease), background 0.2s var(--ease);
}
.tool-input .ti-add:hover { color: var(--ink); background: var(--fill-hover); }
.tool-input .ti-add:active { transform: scale(0.94); }

/* ---------------------------------------------------------------------------
   Spiegel-Achse — Segment-Wähler über dem Dock (nur im Spiegeln-Werkzeug)
   --------------------------------------------------------------------------- */
.mirror-axis {
  position: absolute; bottom: 112px; left: 50%;
  transform: translateX(-50%) translateY(8px);
  z-index: 5;
  display: flex; align-items: center; gap: 10px;
  padding: 6px 8px 6px 14px;
  background: var(--panel);
  -webkit-backdrop-filter: saturate(140%) blur(16px);
  backdrop-filter: saturate(140%) blur(16px);
  border: 1px solid var(--panel-border);
  border-radius: 12px;
  box-shadow: var(--shadow-soft);
  opacity: 0; pointer-events: none;
  transition: opacity 0.3s var(--ease), transform 0.3s var(--ease);
}
.mirror-axis.show { opacity: 1; pointer-events: auto; transform: translateX(-50%) translateY(0); }
.mirror-axis .ma-label {
  font-family: var(--serif); font-style: italic;
  font-size: 15px; color: var(--text-2); flex-shrink: 0;
}
.mirror-axis .ma-seg { display: flex; gap: 2px; }
.mirror-axis .ma-seg button {
  position: relative;
  border: none; background: transparent;
  color: var(--text-2);
  font-family: var(--serif); font-size: 14.5px; letter-spacing: 0.01em;
  padding: 6px 12px; border-radius: 8px; cursor: pointer;
  transition: color 0.2s var(--ease), background 0.2s var(--ease);
}
.mirror-axis .ma-seg button:hover { color: var(--ink); background: var(--fill-hover); }
.mirror-axis .ma-seg button.active { color: var(--ink); background: var(--fill); }

/* Hinweis weicht der Eingabeleiste nach oben aus */
body.tool-entry .hint { bottom: 172px; }
body.tool-entry.kb-open .hint { bottom: calc(var(--kb-h, 0px) + 12px + var(--ti-h, 44px) + 12px); }

/* Onboarding-Hinweis */
.hint {
  position: absolute; bottom: 104px; left: 50%; transform: translateX(-50%) translateY(6px);
  z-index: 4;
  font-family: var(--serif); font-style: italic;
  font-size: 14.5px; color: var(--text-2);
  background: var(--panel);
  -webkit-backdrop-filter: blur(14px); backdrop-filter: blur(14px);
  border: 1px solid var(--panel-border);
  padding: 8px 18px; border-radius: 11px;
  box-shadow: var(--shadow-soft);
  opacity: 0; pointer-events: none;
  transition: opacity 0.5s var(--ease), transform 0.5s var(--ease), bottom 0.3s var(--ease);
  white-space: nowrap;
}
.hint.show { opacity: 1; transform: translateX(-50%) translateY(0); }

/* ---------------------------------------------------------------------------
   Parameter-Regler (Slider) — GeoGebra-artig, im selben stillen Duktus:
   Serifen-Buchstabe, Haarlinien-Bahn, kleiner Knopf, ▷ zum Animieren.
   --------------------------------------------------------------------------- */
.slider-section {
  display: none;
  border-top: 1px solid var(--hair);
  margin-top: 8px; padding-top: 2px;
}
.slider-section.show { display: block; }
.slider-cap {
  font-family: var(--serif); font-style: italic;
  font-size: 12px; color: var(--text-3);
  padding: 9px 8px 4px 8px;
}
.slider-list { display: flex; flex-direction: column; }

.slider {
  padding: 7px 8px 9px;
  border-radius: var(--radius-sm);
  transition: background 0.2s var(--ease);
}
.slider + .slider { border-top: 1px solid var(--hair); }
.slider:hover { background: var(--fill); }

.sl-head { display: flex; align-items: center; gap: 6px; }
.sl-name {
  font-family: var(--serif); font-style: italic;
  font-size: 16px; color: var(--text); line-height: 1;
}
.sl-eq { color: var(--text-3); font-size: 15px; }
.sl-val {
  width: 60px; border: none; outline: none; background: transparent;
  font-family: var(--serif); font-size: 15.5px; color: var(--text);
  font-feature-settings: "onum" 1;
  caret-color: var(--accent);
  border-bottom: 1px solid transparent; padding-bottom: 1px;
  transition: border-color 0.2s;
}
.sl-val:hover { border-bottom-color: var(--hair); }
.sl-val:focus { border-bottom-color: var(--text-3); }
.sl-spacer { flex: 1; }

.sl-btn {
  width: 27px; height: 27px; flex-shrink: 0;
  border: none; background: transparent; color: var(--text-2);
  border-radius: 50%; display: grid; place-items: center; cursor: pointer;
  transition: color 0.18s, background 0.18s, transform 0.12s;
}
.sl-btn:hover { color: var(--ink); background: var(--fill-hover); }
.sl-btn:active { transform: scale(0.9); }
.slider.playing .sl-play { color: var(--ink); }

.sl-track { display: flex; align-items: center; gap: 9px; margin-top: 6px; }
.sl-end {
  font-family: var(--serif); font-size: 11.5px; color: var(--text-3);
  font-feature-settings: "onum" 1; flex-shrink: 0; min-width: 22px;
}
.sl-end.max { text-align: right; }

.sl-range {
  -webkit-appearance: none; appearance: none;
  flex: 1; min-width: 0; height: 16px; background: transparent; cursor: pointer;
}
.sl-range:focus { outline: none; }
.sl-range::-webkit-slider-runnable-track { height: 2px; border-radius: 2px; background: var(--hair); }
.sl-range::-webkit-slider-thumb {
  -webkit-appearance: none; appearance: none;
  width: 13px; height: 13px; margin-top: -5.5px; border-radius: 50%;
  background: var(--panel-solid); border: 1.5px solid var(--ink);
  box-shadow: var(--shadow-soft);
  transition: transform 0.14s var(--ease);
}
.sl-range:hover::-webkit-slider-thumb { transform: scale(1.08); }
.sl-range:active::-webkit-slider-thumb { transform: scale(1.18); }
.sl-range::-moz-range-track { height: 2px; border-radius: 2px; background: var(--hair); }
.sl-range::-moz-range-thumb {
  width: 12px; height: 12px; border-radius: 50%;
  background: var(--panel-solid); border: 1.5px solid var(--ink);
}

.sl-adv {
  display: none; flex-wrap: wrap; align-items: center; gap: 9px 13px;
  padding: 11px 2px 3px;
}
.slider.expanded .sl-adv { display: flex; }
.sl-adv-field { display: flex; align-items: center; gap: 6px; }
.sl-adv-field > span {
  font-family: var(--serif); font-style: italic; font-size: 12px; color: var(--text-3);
}
.sl-adv-field input {
  width: 48px; border: none; outline: none; background: var(--fill);
  border-radius: 6px; padding: 3px 7px;
  font-family: var(--serif); font-size: 13px; color: var(--text);
  font-feature-settings: "onum" 1;
}
.sl-adv-field input:focus { background: var(--fill-hover); }
.sl-mode {
  border: none; background: var(--fill); color: var(--text-2);
  border-radius: 6px; padding: 4px 11px; cursor: pointer;
  font-size: 14px; line-height: 1;
  transition: color 0.18s, background 0.18s;
}
.sl-mode:hover { color: var(--ink); background: var(--fill-hover); }

/* ---------------------------------------------------------------------------
   Mathe-Tastatur — GeoGebra-artig, aber anders geordnet: f(x) zuerst (dies ist
   ein reiner Funktionsplotter), Klammern/Pfeile/Löschen/Enter bleiben fest
   sichtbar rechts, nur die mittlere Seite wechselt (f(x) · 123 · abc · Symbole).
   --------------------------------------------------------------------------- */
.math-kb {
  position: absolute; left: 50%; bottom: 0;
  transform: translateX(-50%) translateY(100%);
  z-index: 8;
  width: min(640px, calc(100vw - 24px));
  display: flex; flex-direction: column; gap: 8px;
  padding: 10px 12px calc(12px + env(safe-area-inset-bottom, 0px));
  background: var(--panel-solid);
  -webkit-backdrop-filter: saturate(140%) blur(16px);
  backdrop-filter: saturate(140%) blur(16px);
  border: 1px solid var(--panel-border);
  border-top-left-radius: var(--radius-lg); border-top-right-radius: var(--radius-lg);
  box-shadow: var(--shadow);
  opacity: 0; pointer-events: none;
  transition: transform 0.32s var(--ease), opacity 0.32s var(--ease);
}
.math-kb.show { opacity: 1; pointer-events: auto; transform: translateX(-50%) translateY(0); }

.mkb-tabs { display: flex; gap: 2px; }
.mkb-tabs button {
  position: relative;
  border: none; background: transparent;
  color: var(--text-2);
  font-family: var(--serif); font-style: italic; font-size: 13.5px;
  padding: 6px 12px 8px; border-radius: 8px;
  cursor: pointer;
  transition: color 0.2s var(--ease);
}
.mkb-tabs button:hover { color: var(--ink); }
.mkb-tabs button.active { color: var(--ink); }
.mkb-tabs button.active::after {
  content: ''; position: absolute; left: 10px; right: 10px; bottom: 3px;
  height: 1.5px; background: var(--ink); border-radius: 1px;
}

.mkb-pages { position: relative; }
.mkb-page {
  display: none;
  grid-template-columns: repeat(6, 1fr);
  gap: 6px;
}
.mkb-page.active { display: grid; }

.mkb-page button, .mkb-nav button {
  border: none; background: var(--fill); color: var(--text);
  font-family: var(--serif); font-size: 15px; letter-spacing: 0.01em;
  padding: 9px 4px; border-radius: var(--radius-sm);
  cursor: pointer;
  transition: background 0.15s var(--ease), color 0.15s var(--ease), transform 0.1s var(--ease);
}
.mkb-page button:hover, .mkb-nav button:hover { background: var(--fill-hover); color: var(--ink); }
.mkb-page button:active, .mkb-nav button:active { transform: scale(0.94); }
.mkb-page button.mkb-var { font-style: italic; color: var(--accent); }

.mkb-nav {
  display: grid; grid-template-columns: repeat(6, 1fr);
  gap: 6px;
}
.mkb-nav .mkb-back { color: var(--danger); }
.mkb-nav .mkb-close { color: var(--text-2); font-size: 17px; }
.mkb-nav .mkb-close:hover { color: var(--ink); }

@media (max-width: 520px) {
  .math-kb { width: 100vw; border-radius: 0; }
  .mkb-page button, .mkb-nav button { padding: 11px 3px; font-size: 14px; }
}