/* ===== Reset & Base ===== */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --bg-primary: #080910;
  --bg-secondary: #10131d;
  --panel: #151824;
  --panel-strong: #1b1f2d;
  --panel-soft: rgba(255, 255, 255, 0.045);
  --surface: rgba(255, 255, 255, 0.065);
  --surface-hover: rgba(255, 255, 255, 0.105);
  --border: rgba(226, 232, 240, 0.095);
  --border-strong: rgba(226, 232, 240, 0.16);
  --text-primary: #f7f8fb;
  --text-secondary: #aeb5c4;
  --text-muted: #6f7788;
  --heart-red: #ec3d72;
  --heart-red-bright: #ff5f8c;
  --heart-glow: rgba(236, 61, 114, 0.28);
  --heart-glow-strong: rgba(236, 61, 114, 0.55);
  --accent: #ec3d72;
  --accent-dim: rgba(236, 61, 114, 0.18);
  --ok: #42d392;
  --danger: #ff6b7a;
  --shadow: 0 28px 80px rgba(0, 0, 0, 0.46);
  --card-radius: 8px;
  --control-radius: 8px;
  --font: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
}

body {
  font-family: var(--font);
  background:
    radial-gradient(circle at 50% -20%, rgba(236, 61, 114, 0.14), transparent 34rem),
    linear-gradient(180deg, #0b0d15 0%, var(--bg-primary) 48%, #06070d 100%);
  color: var(--text-primary);
  min-height: 100vh;
  height: 100vh;
  height: 100dvh;
  display: flex;
  align-items: flex-start;
  justify-content: center;
  overflow: hidden;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

button,
input {
  font: inherit;
}

button {
  -webkit-tap-highlight-color: transparent;
}

button:focus-visible,
input:focus-visible {
  outline: 2px solid rgba(255, 95, 140, 0.72);
  outline-offset: 3px;
}

/* ===== App Container ===== */
.app {
  width: min(100%, 480px);
  height: 100vh;
  height: 100dvh;
  max-height: 100vh;
  max-height: 100dvh;
  display: flex;
  flex-direction: column;
  align-items: stretch;
  padding: 22px 18px 82px;
  position: relative;
  gap: 14px;
  overflow: hidden;
  z-index: 1;
}

.main {
  width: 100%;
  min-height: 0;
  display: flex;
  flex-direction: column;
  align-items: stretch;
  gap: 10px;
  position: relative;
  z-index: 1;
}

/* ===== Background Pulse ===== */
.bg-pulse {
  position: fixed;
  top: 28%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 520px;
  height: 520px;
  border-radius: 50%;
  background: radial-gradient(circle, var(--heart-glow) 0%, transparent 68%);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.1s ease;
  z-index: 0;
}

.bg-pulse.active {
  opacity: 1;
  animation: bgPulseAnim 0.6s ease-out;
}

@keyframes bgPulseAnim {
  0% {
    transform: translate(-50%, -50%) scale(0.8);
    opacity: 0.75;
  }

  100% {
    transform: translate(-50%, -50%) scale(1.24);
    opacity: 0;
  }
}

/* ===== Header ===== */
.header {
  text-align: center;
  position: relative;
  z-index: 1;
}

.header h1 {
  font-size: 1.82rem;
  font-weight: 800;
  line-height: 1.05;
  letter-spacing: 0;
  color: var(--heart-red-bright);
  text-shadow: 0 0 28px rgba(236, 61, 114, 0.32);
}

.subtitle {
  font-size: 0.78rem;
  color: var(--text-secondary);
  margin-top: 0.35rem;
  font-weight: 400;
  letter-spacing: 0;
}

/* ===== Segmented Controls ===== */
.mode-toggle,
.connection-mode-toggle {
  display: grid;
  gap: 4px;
  background: rgba(255, 255, 255, 0.055);
  border: 1px solid var(--border);
  border-radius: var(--control-radius);
  padding: 4px;
  position: relative;
  z-index: 1;
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.04);
}

.mode-toggle {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.connection-mode-toggle {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.mode-btn,
.conn-mode-btn {
  min-height: 36px;
  background: transparent;
  border: 0;
  color: var(--text-secondary);
  border-radius: 6px;
  cursor: pointer;
  transition: background 0.18s ease, color 0.18s ease, box-shadow 0.18s ease;
  white-space: nowrap;
}

.mode-btn {
  font-size: 0.84rem;
  font-weight: 700;
  padding: 0 0.55rem;
}

.conn-mode-btn {
  font-size: 0.78rem;
  font-weight: 700;
  padding: 0 0.4rem;
}

.mode-btn.active,
.conn-mode-btn.active {
  background: linear-gradient(180deg, rgba(255, 95, 140, 0.26), rgba(236, 61, 114, 0.18));
  color: #ffd3de;
  box-shadow: inset 0 0 0 1px rgba(255, 95, 140, 0.2), 0 8px 24px rgba(236, 61, 114, 0.16);
}

.mode-btn:hover:not(.active),
.conn-mode-btn:hover:not(.active) {
  background: rgba(255, 255, 255, 0.055);
  color: var(--text-primary);
}

/* ===== Primary Measurement Area ===== */
.heart-container,
.bpm-display,
.slider-container,
.presets,
.volume-container,
.play-btn,
.sensor-btn,
.sensor-status,
.connection-mode-toggle,
.distance-settings-toggle,
.distance-advanced,
.wifi-settings,
.distance-calibration,
.distance-display,
.distance-mapping {
  position: relative;
  z-index: 1;
}

.heart-container {
  width: 100%;
  height: 108px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-top: 4px;
  background:
    radial-gradient(circle at 50% 48%, rgba(236, 61, 114, 0.13), transparent 72px),
    linear-gradient(180deg, rgba(255, 255, 255, 0.035), transparent);
  border: 1px solid var(--border);
  border-radius: var(--card-radius);
}

.heart-icon {
  width: 68px;
  height: 68px;
  fill: var(--heart-red);
  filter: drop-shadow(0 0 22px var(--heart-glow));
  transition: transform 0.1s ease;
  z-index: 2;
}

.heart-icon.beat {
  animation: heartBeat 0.3s ease-out;
}

@keyframes heartBeat {
  0% {
    transform: scale(1);
  }

  15% {
    transform: scale(1.28);
  }

  30% {
    transform: scale(1.09);
  }

  45% {
    transform: scale(1.17);
  }

  100% {
    transform: scale(1);
  }
}

.heart-glow {
  position: absolute;
  width: 126px;
  height: 126px;
  border-radius: 50%;
  background: radial-gradient(circle, var(--heart-glow-strong) 0%, transparent 68%);
  opacity: 0;
  z-index: 1;
  transition: opacity 0.15s ease;
}

.heart-glow.active {
  opacity: 1;
  animation: glowPulse 0.5s ease-out;
}

@keyframes glowPulse {
  0% {
    transform: scale(0.82);
    opacity: 0.9;
  }

  100% {
    transform: scale(1.55);
    opacity: 0;
  }
}

.heart-ring {
  position: absolute;
  width: 100px;
  height: 100px;
  border-radius: 50%;
  border: 1px solid var(--heart-glow);
  opacity: 0;
  z-index: 0;
}

.heart-ring.active {
  animation: ringExpand 0.8s ease-out;
}

@keyframes ringExpand {
  0% {
    transform: scale(0.8);
    opacity: 0.8;
    border-width: 2px;
  }

  100% {
    transform: scale(2);
    opacity: 0;
    border-width: 0.5px;
  }
}

.bpm-display {
  display: flex;
  align-items: baseline;
  justify-content: center;
  gap: 0.55rem;
  margin-top: -4px;
}

.bpm-value {
  font-size: clamp(4.3rem, 19vw, 5.8rem);
  font-weight: 900;
  letter-spacing: 0;
  line-height: 0.9;
  color: var(--text-primary);
  text-shadow: 0 20px 34px rgba(0, 0, 0, 0.34);
}

.bpm-label {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text-secondary);
  letter-spacing: 0.08em;
}

/* ===== Range Inputs ===== */
.slider-container,
.volume-container {
  display: flex;
  align-items: center;
}

.slider-container {
  gap: 0.75rem;
  width: 100%;
  padding: 0 4px;
}

.slider-min,
.slider-max,
.mapping-range span {
  font-size: 0.72rem;
  color: var(--text-muted);
  font-weight: 700;
  min-width: 28px;
  text-align: center;
}

.bpm-slider,
.volume-slider,
.calibration-slider,
.mapping-slider {
  -webkit-appearance: none;
  appearance: none;
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.105), rgba(255, 255, 255, 0.05));
  border-radius: 999px;
  outline: none;
  cursor: pointer;
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.26);
}

.bpm-slider {
  flex: 1;
  height: 8px;
}

.volume-slider,
.calibration-slider,
.mapping-slider {
  height: 6px;
}

.volume-slider,
.mapping-slider {
  flex: 1;
}

.bpm-slider::-webkit-slider-thumb,
.volume-slider::-webkit-slider-thumb,
.calibration-slider::-webkit-slider-thumb,
.mapping-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  border-radius: 50%;
  cursor: pointer;
  background: var(--heart-red-bright);
  border: 2px solid rgba(255, 255, 255, 0.22);
  box-shadow: 0 0 0 5px rgba(236, 61, 114, 0.12), 0 8px 18px rgba(0, 0, 0, 0.38);
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.bpm-slider::-webkit-slider-thumb {
  width: 24px;
  height: 24px;
}

.volume-slider::-webkit-slider-thumb,
.calibration-slider::-webkit-slider-thumb,
.mapping-slider::-webkit-slider-thumb {
  width: 18px;
  height: 18px;
}

.bpm-slider::-webkit-slider-thumb:hover,
.volume-slider::-webkit-slider-thumb:hover,
.calibration-slider::-webkit-slider-thumb:hover,
.mapping-slider::-webkit-slider-thumb:hover {
  transform: scale(1.08);
  box-shadow: 0 0 0 7px rgba(236, 61, 114, 0.16), 0 8px 22px rgba(0, 0, 0, 0.42);
}

.bpm-slider::-moz-range-thumb,
.volume-slider::-moz-range-thumb,
.calibration-slider::-moz-range-thumb,
.mapping-slider::-moz-range-thumb {
  border-radius: 50%;
  cursor: pointer;
  background: var(--heart-red-bright);
  border: 2px solid rgba(255, 255, 255, 0.22);
  box-shadow: 0 0 0 5px rgba(236, 61, 114, 0.12), 0 8px 18px rgba(0, 0, 0, 0.38);
}

.bpm-slider::-moz-range-thumb {
  width: 22px;
  height: 22px;
}

.volume-slider::-moz-range-thumb,
.calibration-slider::-moz-range-thumb,
.mapping-slider::-moz-range-thumb {
  width: 16px;
  height: 16px;
}

/* ===== Presets ===== */
.presets {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 7px;
  width: 100%;
}

.preset-btn {
  min-height: 52px;
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.075), rgba(255, 255, 255, 0.045));
  border: 1px solid var(--border);
  border-radius: var(--card-radius);
  padding: 0.58rem 0.35rem;
  color: var(--text-secondary);
  font-size: 0.72rem;
  font-weight: 700;
  cursor: pointer;
  transition: transform 0.18s ease, background 0.18s ease, border-color 0.18s ease, color 0.18s ease;
  text-align: center;
  line-height: 1.35;
}

.preset-btn small {
  display: inline-block;
  margin-top: 2px;
  font-size: 1rem;
  font-weight: 800;
  color: var(--text-primary);
}

.preset-btn:hover {
  background: var(--surface-hover);
  border-color: rgba(255, 95, 140, 0.26);
  transform: translateY(-1px);
}

.preset-btn.active {
  background: linear-gradient(180deg, rgba(255, 95, 140, 0.22), rgba(236, 61, 114, 0.13));
  border-color: rgba(255, 95, 140, 0.35);
  color: #ffd3de;
}

.preset-btn.active small {
  color: var(--heart-red-bright);
}

/* ===== Volume ===== */
.volume-container {
  align-self: center;
  gap: 0.75rem;
  width: min(100%, 270px);
  padding: 6px 0 2px;
}

.volume-icon {
  color: var(--text-secondary);
  flex-shrink: 0;
  width: 18px;
  height: 18px;
}

/* ===== Action Buttons ===== */
.play-btn {
  align-self: center;
  width: 68px;
  height: 68px;
  border-radius: 50%;
  background: linear-gradient(145deg, #ff628f, #dc2d63 62%, #b91f50);
  border: 1px solid rgba(255, 255, 255, 0.18);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 18px 44px rgba(236, 61, 114, 0.32), inset 0 1px 0 rgba(255, 255, 255, 0.22);
  transition: transform 0.18s ease, box-shadow 0.18s ease;
}

.play-btn:hover {
  transform: translateY(-1px) scale(1.04);
  box-shadow: 0 22px 54px rgba(236, 61, 114, 0.42), inset 0 1px 0 rgba(255, 255, 255, 0.24);
}

.play-btn:active {
  transform: scale(0.96);
}

.play-icon,
.stop-icon {
  width: 28px;
  height: 28px;
  fill: white;
}

.play-icon {
  margin-left: 3px;
}

.sensor-btn {
  min-height: 48px;
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.6rem;
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.08), rgba(255, 255, 255, 0.05));
  border: 1px solid var(--border-strong);
  border-radius: var(--card-radius);
  padding: 0.8rem 1rem;
  color: var(--text-primary);
  font-size: 0.93rem;
  font-weight: 800;
  cursor: pointer;
  transition: transform 0.18s ease, background 0.18s ease, border-color 0.18s ease;
}

.sensor-btn:hover {
  background: var(--surface-hover);
  border-color: rgba(255, 95, 140, 0.36);
  transform: translateY(-1px);
}

.sensor-btn:disabled {
  opacity: 0.48;
  cursor: not-allowed;
  transform: none;
}

.sensor-icon {
  width: 20px;
  height: 20px;
  fill: var(--heart-red-bright);
}

/* ===== Sensor Status ===== */
.sensor-status {
  width: fit-content;
  display: flex;
  align-items: center;
  gap: 0.48rem;
  padding: 0.35rem 0.6rem;
  color: var(--text-secondary);
}

.status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--text-muted);
  box-shadow: 0 0 0 4px rgba(174, 181, 196, 0.08);
}

.status-dot.connected {
  background: var(--ok);
  box-shadow: 0 0 0 4px rgba(66, 211, 146, 0.12), 0 0 14px rgba(66, 211, 146, 0.5);
  animation: dotPulse 2s ease-in-out infinite;
}

.status-dot.error {
  background: var(--danger);
  box-shadow: 0 0 0 4px rgba(255, 107, 122, 0.12);
}

@keyframes dotPulse {
  0%,
  100% {
    opacity: 1;
  }

  50% {
    opacity: 0.55;
  }
}

.status-text {
  font-size: 0.78rem;
  font-weight: 700;
}

/* ===== Settings Panels ===== */
.wifi-settings,
.distance-calibration,
.distance-display,
.distance-mapping {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  width: 100%;
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.07), rgba(255, 255, 255, 0.038)),
    var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--card-radius);
  padding: 0.85rem;
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.04);
}

.wifi-instructions {
  font-size: 0.82rem;
  color: var(--text-secondary);
  line-height: 1.65;
}

.wifi-instructions p {
  margin: 0.25rem 0;
}

.wifi-instructions strong {
  color: var(--heart-red-bright);
}

.wifi-instructions code {
  display: inline-block;
  max-width: 100%;
  overflow-wrap: anywhere;
  background: rgba(0, 0, 0, 0.32);
  border: 1px solid rgba(255, 255, 255, 0.055);
  padding: 0.18rem 0.42rem;
  border-radius: 5px;
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
  color: var(--text-primary);
}

.wifi-input-group {
  display: flex;
  flex-direction: column;
  gap: 0.42rem;
}

.wifi-input-group label {
  font-size: 0.76rem;
  color: var(--text-secondary);
  font-weight: 700;
}

.wifi-input-group input {
  width: 100%;
  min-height: 44px;
  background: rgba(0, 0, 0, 0.34);
  border: 1px solid rgba(255, 255, 255, 0.075);
  border-radius: var(--control-radius);
  padding: 0.6rem 0.75rem;
  color: var(--text-primary);
  font-size: 0.94rem;
  outline: none;
  transition: border-color 0.18s ease, background 0.18s ease;
}

.wifi-input-group input:focus {
  background: rgba(0, 0, 0, 0.42);
  border-color: rgba(255, 95, 140, 0.58);
}

.calibration-title,
.mapping-title {
  font-size: 0.93rem;
  font-weight: 800;
  color: var(--text-primary);
  text-align: left;
}

.calibration-sliders,
.mapping-sliders {
  display: flex;
  flex-direction: column;
  gap: 0.85rem;
}

.calibration-item,
.mapping-item {
  display: flex;
  flex-direction: column;
  gap: 0.45rem;
}

.calibration-label,
.mapping-label {
  font-size: 0.78rem;
  color: var(--text-secondary);
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.75rem;
  font-weight: 700;
}

.calibration-label span,
.mapping-bpm {
  color: var(--heart-red-bright);
  font-weight: 800;
}

.mapping-range {
  display: flex;
  align-items: center;
  gap: 0.55rem;
}

.calibration-reset {
  min-height: 42px;
  background: rgba(255, 255, 255, 0.075);
  border: 1px solid var(--border);
  border-radius: var(--control-radius);
  padding: 0.55rem 0.75rem;
  color: var(--text-secondary);
  font-size: 0.8rem;
  font-weight: 800;
  cursor: pointer;
  transition: background 0.18s ease, color 0.18s ease, border-color 0.18s ease;
  position: relative;
  z-index: 10;
  pointer-events: auto;
}

.calibration-reset:hover {
  background: var(--accent-dim);
  border-color: rgba(255, 95, 140, 0.28);
  color: #ffd3de;
}

/* ===== Distance Display ===== */
.distance-display {
  align-items: stretch;
  text-align: center;
}

.distance-value-container {
  display: flex;
  align-items: baseline;
  justify-content: center;
  gap: 0.35rem;
}

.distance-value {
  font-size: 2.25rem;
  font-weight: 900;
  color: var(--heart-red-bright);
  line-height: 1;
}

.distance-unit {
  font-size: 1rem;
  color: var(--text-secondary);
  font-weight: 800;
}

.distance-label {
  font-size: 0.76rem;
  color: var(--text-secondary);
  font-weight: 700;
}

.distance-bar-container {
  width: 100%;
  height: 8px;
  background: rgba(255, 255, 255, 0.07);
  border-radius: 999px;
  overflow: hidden;
}

.distance-bar {
  height: 100%;
  background: linear-gradient(90deg, #ff789e, var(--heart-red-bright));
  border-radius: 999px;
  transition: width 0.3s ease;
  width: 0%;
}

/* ===== ECG Container ===== */
.ecg-container {
  position: fixed;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 72px;
  opacity: 0.18;
  z-index: 0;
  pointer-events: none;
  mask-image: linear-gradient(90deg, transparent 0%, #000 12%, #000 88%, transparent 100%);
}

#ecgCanvas {
  width: 100%;
  height: 100%;
}

.hidden {
  display: none !important;
}

/* ===== No-Page-Scroll Mode Layouts ===== */
.app:has(#pulseSensorBtn:not(.hidden)) .heart-container {
  height: 96px;
}

.app:has(#pulseSensorBtn:not(.hidden)) .bpm-value {
  font-size: clamp(4rem, 18vw, 5.3rem);
}

.app:has(#distanceCalibration:not(.hidden)) {
  padding-top: 16px;
  padding-bottom: 54px;
  gap: 10px;
}

.app:has(#distanceCalibration:not(.hidden)) .header h1 {
  font-size: 1.55rem;
}

.app:has(#distanceCalibration:not(.hidden)) .subtitle {
  display: none;
}

.app:has(#distanceCalibration:not(.hidden)) .mode-btn,
.app:has(#distanceCalibration:not(.hidden)) .conn-mode-btn {
  min-height: 34px;
}

.app:has(#distanceCalibration:not(.hidden)) .main {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  align-content: start;
  gap: 8px;
}

.app:has(#distanceCalibration:not(.hidden)) .heart-container {
  display: none;
}

.app:has(#distanceCalibration:not(.hidden)) .bpm-display,
.app:has(#distanceCalibration:not(.hidden)) .volume-container,
.app:has(#distanceCalibration:not(.hidden)) .connection-mode-toggle,
.app:has(#distanceCalibration:not(.hidden)) .sensor-btn,
.app:has(#distanceCalibration:not(.hidden)) .sensor-status,
.app:has(#distanceCalibration:not(.hidden)) .wifi-settings,
.app:has(#distanceCalibration:not(.hidden)) .distance-mapping {
  grid-column: 1 / -1;
}

.app:has(#distanceCalibration:not(.hidden)) .bpm-display {
  margin-top: 0;
}

.app:has(#distanceCalibration:not(.hidden)) .bpm-value {
  font-size: clamp(3.5rem, 16vw, 4.7rem);
}

.app:has(#distanceCalibration:not(.hidden)) .bpm-label {
  font-size: 0.82rem;
}

.app:has(#distanceCalibration:not(.hidden)) .volume-container {
  width: min(100%, 230px);
  padding: 0;
}

.app:has(#distanceCalibration:not(.hidden)) .sensor-status {
  padding: 0.1rem 0.25rem;
}

.app:has(#distanceCalibration:not(.hidden)) .wifi-settings,
.app:has(#distanceCalibration:not(.hidden)) .distance-calibration,
.app:has(#distanceCalibration:not(.hidden)) .distance-display,
.app:has(#distanceCalibration:not(.hidden)) .distance-mapping {
  gap: 0.55rem;
  padding: 0.7rem;
}

.app:has(#distanceCalibration:not(.hidden)) .wifi-instructions {
  font-size: 0.76rem;
  line-height: 1.45;
}

.app:has(#distanceCalibration:not(.hidden)) .wifi-input-group input {
  min-height: 38px;
  padding: 0.48rem 0.62rem;
  font-size: 0.86rem;
}

.app:has(#distanceCalibration:not(.hidden)) .calibration-title,
.app:has(#distanceCalibration:not(.hidden)) .mapping-title {
  font-size: 0.82rem;
}

.app:has(#distanceCalibration:not(.hidden)) .calibration-sliders,
.app:has(#distanceCalibration:not(.hidden)) .mapping-sliders {
  gap: 0.54rem;
}

.app:has(#distanceCalibration:not(.hidden)) .calibration-item,
.app:has(#distanceCalibration:not(.hidden)) .mapping-item {
  gap: 0.3rem;
}

.app:has(#distanceCalibration:not(.hidden)) .calibration-label,
.app:has(#distanceCalibration:not(.hidden)) .mapping-label {
  font-size: 0.71rem;
}

.app:has(#distanceCalibration:not(.hidden)) .calibration-reset {
  min-height: 34px;
  padding: 0.35rem 0.55rem;
}

.app:has(#distanceCalibration:not(.hidden)) .distance-display {
  justify-content: center;
}

.app:has(#distanceCalibration:not(.hidden)) .distance-value {
  font-size: 1.9rem;
}

.app:has(#distanceCalibration:not(.hidden)) .distance-label {
  font-size: 0.69rem;
}

.app:has(#distanceCalibration:not(.hidden)) .mapping-range {
  gap: 0.4rem;
}

.app:has(#distanceCalibration:not(.hidden)) .mapping-range span {
  min-width: 24px;
  font-size: 0.67rem;
}

.app:has(#distanceCalibration:not(.hidden)) .ecg-container {
  height: 54px;
}

/* ===== Responsive ===== */
@media (min-width: 768px) {
  body {
    align-items: center;
    padding: 24px;
  }

  .app {
    width: min(100%, 430px);
    min-height: 0;
    padding: 28px 28px 42px;
    border-radius: 8px;
    background:
      linear-gradient(180deg, rgba(255, 255, 255, 0.055), rgba(255, 255, 255, 0.025)),
      var(--bg-secondary);
    border: 1px solid var(--border);
    box-shadow: var(--shadow);
  }

  .app:has(#distanceCalibration:not(.hidden)) {
    width: min(100%, 560px);
  }

  .ecg-container {
    opacity: 0.18;
  }
}

@media (max-width: 380px) {
  .app {
    padding-left: 14px;
    padding-right: 14px;
  }

  .mode-btn {
    font-size: 0.78rem;
    padding: 0 0.3rem;
  }

  .preset-btn {
    font-size: 0.66rem;
  }

  .preset-btn small {
    font-size: 0.92rem;
  }

  .sensor-btn {
    font-size: 0.86rem;
  }
}

@media (max-height: 850px) {
  .app:has(#distanceCalibration:not(.hidden)) {
    padding-top: 10px;
    padding-bottom: 34px;
    gap: 8px;
  }

  .app:has(#distanceCalibration:not(.hidden)) .header h1 {
    font-size: 1.42rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .mode-btn,
  .app:has(#distanceCalibration:not(.hidden)) .conn-mode-btn {
    min-height: 30px;
  }

  .app:has(#distanceCalibration:not(.hidden)) .main {
    gap: 6px;
  }

  .app:has(#distanceCalibration:not(.hidden)) .bpm-value {
    font-size: clamp(3.05rem, 14vw, 4rem);
  }

  .app:has(#distanceCalibration:not(.hidden)) .bpm-label {
    font-size: 0.76rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .volume-container {
    display: none;
  }

  .app:has(#distanceCalibration:not(.hidden)) .sensor-btn {
    min-height: 42px;
    padding: 0.58rem 0.8rem;
    font-size: 0.84rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .sensor-status {
    padding: 0;
  }

  .app:has(#distanceCalibration:not(.hidden)) .wifi-settings,
  .app:has(#distanceCalibration:not(.hidden)) .distance-calibration,
  .app:has(#distanceCalibration:not(.hidden)) .distance-display,
  .app:has(#distanceCalibration:not(.hidden)) .distance-mapping {
    gap: 0.42rem;
    padding: 0.56rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .wifi-instructions {
    font-size: 0.7rem;
    line-height: 1.34;
  }

  .app:has(#distanceCalibration:not(.hidden)) .wifi-input-group {
    gap: 0.25rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .wifi-input-group label {
    font-size: 0.68rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .wifi-input-group input {
    min-height: 34px;
    padding: 0.38rem 0.52rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .calibration-title,
  .app:has(#distanceCalibration:not(.hidden)) .mapping-title {
    font-size: 0.76rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .calibration-sliders,
  .app:has(#distanceCalibration:not(.hidden)) .mapping-sliders {
    gap: 0.34rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .calibration-label,
  .app:has(#distanceCalibration:not(.hidden)) .mapping-label {
    font-size: 0.66rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .calibration-reset {
    min-height: 30px;
    font-size: 0.72rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .distance-value {
    font-size: 1.65rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .distance-label {
    font-size: 0.64rem;
  }
}

@media (max-height: 740px) {
  .app:has(#distanceCalibration:not(.hidden)) {
    padding-top: 8px;
    padding-bottom: 22px;
  }

  .app:has(#distanceCalibration:not(.hidden)) .header h1 {
    font-size: 1.32rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .sensor-status {
    display: none;
  }

  .app:has(#distanceCalibration:not(.hidden)) .wifi-settings,
  .app:has(#distanceCalibration:not(.hidden)) .distance-calibration,
  .app:has(#distanceCalibration:not(.hidden)) .distance-display,
  .app:has(#distanceCalibration:not(.hidden)) .distance-mapping {
    padding: 0.5rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .distance-bar-container {
    height: 6px;
  }
}

@media (max-height: 700px) and (min-width: 768px) {
  body {
    align-items: flex-start;
  }

  .app {
    margin-top: 0;
  }
}

.distance-settings-toggle {
  width: 100%;
  min-height: 44px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.7rem 0.85rem;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border);
  border-radius: var(--control-radius);
  color: var(--text-secondary);
  font-size: 0.82rem;
  font-weight: 800;
  cursor: pointer;
}

.distance-settings-toggle:hover,
.distance-settings-toggle.active {
  color: var(--text-primary);
  background: var(--surface-hover);
  border-color: rgba(255, 95, 140, 0.28);
}

.settings-toggle-icon {
  color: var(--heart-red-bright);
  font-size: 1.1rem;
  line-height: 1;
}

.distance-advanced {
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

/* ===== Desktop workspace ===== */
@media (min-width: 900px) {
  body {
    align-items: center;
    padding: 28px;
    overflow-y: auto;
  }

  .app,
  .app:has(#distanceCalibration:not(.hidden)) {
    width: min(100%, 1180px);
    height: auto;
    min-height: min(720px, calc(100vh - 56px));
    max-height: none;
    display: grid;
    grid-template-columns: minmax(240px, 1fr) minmax(520px, 1.35fr);
    grid-template-rows: auto minmax(0, 1fr);
    align-items: center;
    gap: 24px 36px;
    padding: 30px 34px 84px;
    overflow: visible;
    border-radius: 16px;
  }

  .header {
    grid-column: 1;
    grid-row: 1;
    text-align: left;
  }

  .header h1,
  .app:has(#distanceCalibration:not(.hidden)) .header h1 {
    font-size: 2rem;
  }

  .subtitle,
  .app:has(#distanceCalibration:not(.hidden)) .subtitle {
    display: block;
    font-size: 0.8rem;
  }

  .mode-toggle {
    grid-column: 2;
    grid-row: 1;
    width: 100%;
    justify-self: end;
  }

  .mode-btn,
  .app:has(#distanceCalibration:not(.hidden)) .mode-btn {
    min-height: 44px;
    font-size: 0.88rem;
  }

  .main,
  .app:has(#distanceCalibration:not(.hidden)) .main {
    grid-column: 1 / -1;
    grid-row: 2;
    width: 100%;
    min-height: 470px;
    display: grid;
    grid-template-columns: minmax(340px, 0.9fr) minmax(460px, 1.1fr);
    grid-template-rows: auto auto auto auto 1fr;
    align-items: center;
    align-content: stretch;
    gap: 16px 32px;
  }

  .heart-container,
  .app:has(#pulseSensorBtn:not(.hidden)) .heart-container,
  .app:has(#distanceCalibration:not(.hidden)) .heart-container {
    grid-column: 1;
    grid-row: 1 / -1;
    display: flex;
    height: 100%;
    min-height: 430px;
    margin: 0;
    border-radius: 12px;
    background:
      radial-gradient(circle at 50% 44%, rgba(236, 61, 114, 0.2), transparent 150px),
      linear-gradient(145deg, rgba(255, 255, 255, 0.055), rgba(255, 255, 255, 0.018));
  }

  .heart-icon {
    width: 148px;
    height: 148px;
  }

  .heart-glow {
    width: 260px;
    height: 260px;
  }

  .heart-ring {
    width: 190px;
    height: 190px;
  }

  .bpm-display,
  .app:has(#distanceCalibration:not(.hidden)) .bpm-display {
    grid-column: 2;
    grid-row: 1;
    justify-content: flex-start;
    margin: 0;
    padding-top: 6px;
  }

  .bpm-value,
  .app:has(#pulseSensorBtn:not(.hidden)) .bpm-value,
  .app:has(#distanceCalibration:not(.hidden)) .bpm-value {
    font-size: clamp(5.8rem, 8vw, 7.6rem);
  }

  .bpm-label,
  .app:has(#distanceCalibration:not(.hidden)) .bpm-label {
    font-size: 1rem;
  }

  .slider-container {
    grid-column: 2;
    grid-row: 2;
  }

  .presets {
    grid-column: 2;
    grid-row: 3;
    gap: 10px;
  }

  .preset-btn {
    min-height: 72px;
    font-size: 0.76rem;
  }

  .preset-btn small {
    font-size: 1.12rem;
  }

  .volume-container,
  .app:has(#distanceCalibration:not(.hidden)) .volume-container {
    grid-column: 2;
    grid-row: 4;
    justify-self: start;
    align-self: center;
    width: min(100%, 320px);
    padding: 0;
  }

  .play-btn {
    grid-column: 2;
    grid-row: 5;
    justify-self: start;
    align-self: start;
    width: 78px;
    height: 78px;
  }

  .sensor-btn {
    grid-column: 2;
    width: min(100%, 460px);
    min-height: 54px;
  }

  .sensor-status {
    grid-column: 2;
  }

  .connection-mode-toggle {
    grid-column: 2;
    width: 100%;
  }

  .wifi-settings,
  .distance-calibration,
  .distance-display,
  .distance-mapping,
  .app:has(#distanceCalibration:not(.hidden)) .wifi-settings,
  .app:has(#distanceCalibration:not(.hidden)) .distance-calibration,
  .app:has(#distanceCalibration:not(.hidden)) .distance-display,
  .app:has(#distanceCalibration:not(.hidden)) .distance-mapping {
    border-radius: 10px;
    padding: 1rem;
    gap: 0.8rem;
  }

  /* Pulse sensor: keep the measurement visual on the left and actions on the right. */
  .app:has(#pulseSensorBtn:not(.hidden)) .pulse-placeholder {
    display: none;
  }

  .app:has(#pulseSensorBtn:not(.hidden)) .sensor-btn {
    grid-row: 3;
    align-self: end;
  }

  .app:has(#pulseSensorBtn:not(.hidden)) .sensor-status {
    grid-row: 4;
    align-self: start;
  }

  /* Distance sensor becomes a three-column control desk. */
  .app:has(#distanceCalibration:not(.hidden)) {
    width: min(100%, 1320px);
    grid-template-columns: minmax(220px, 0.8fr) minmax(540px, 1.4fr);
  }

  .app:has(#distanceCalibration:not(.hidden)) .main {
    min-height: 500px;
    grid-template-columns: minmax(300px, 0.85fr) minmax(520px, 1.15fr);
    grid-template-rows: auto auto auto auto 1fr;
    align-items: start;
    gap: 14px 18px;
  }

  .app:has(#distanceCalibration:not(.hidden)) .heart-container {
    grid-column: 1;
    grid-row: 1 / 4;
    min-height: 300px;
  }

  .app:has(#distanceCalibration:not(.hidden)) .heart-icon {
    width: 108px;
    height: 108px;
  }

  .app:has(#distanceCalibration:not(.hidden)) .bpm-display {
    grid-column: 1;
    grid-row: 4;
    justify-content: center;
  }

  .app:has(#distanceCalibration:not(.hidden)) .bpm-value {
    font-size: clamp(4.5rem, 6vw, 6rem);
  }

  .app:has(#distanceCalibration:not(.hidden)) .volume-container {
    grid-column: 1;
    grid-row: 5;
    display: flex;
    justify-self: center;
    width: 86%;
  }

  .app:has(#distanceCalibration:not(.hidden)) .connection-mode-toggle {
    grid-column: 2;
    grid-row: 1;
  }

  .app:has(#distanceCalibration:not(.hidden)) .sensor-btn {
    grid-column: 2;
    grid-row: 2;
    width: 100%;
  }

  .app:has(#distanceCalibration:not(.hidden)) .sensor-status {
    grid-column: 2;
    grid-row: 3;
    display: flex;
  }

  .app:has(#distanceCalibration:not(.hidden)) .wifi-settings {
    grid-column: 2;
    grid-row: 4;
  }

  .app:has(#distanceCalibration:not(.hidden)) .distance-display {
    grid-column: 2;
    grid-row: 4;
    align-self: stretch;
  }

  .app:has(#distanceCalibration:not(.hidden)) .distance-settings-toggle {
    grid-column: 2;
    grid-row: 5;
  }

  .app:has(#distanceAdvanced:not(.hidden)) .main {
    grid-template-columns: minmax(280px, 0.75fr) minmax(300px, 0.8fr) minmax(400px, 1.15fr);
  }

  .app:has(#distanceAdvanced:not(.hidden)) .distance-settings-toggle {
    grid-column: 3;
    grid-row: 1;
  }

  .app:has(#distanceAdvanced:not(.hidden)) .distance-advanced {
    grid-column: 3;
    grid-row: 2 / 6;
  }

  .app:has(#distanceAdvanced:not(.hidden)) .distance-calibration,
  .app:has(#distanceAdvanced:not(.hidden)) .distance-mapping {
    display: flex;
  }

  .app:has(#distanceCalibration:not(.hidden)) .calibration-title,
  .app:has(#distanceCalibration:not(.hidden)) .mapping-title {
    font-size: 0.9rem;
  }

  .app:has(#distanceCalibration:not(.hidden)) .calibration-label,
  .app:has(#distanceCalibration:not(.hidden)) .mapping-label {
    font-size: 0.76rem;
  }

  .ecg-container,
  .app:has(#distanceCalibration:not(.hidden)) .ecg-container {
    height: 82px;
    opacity: 0.22;
  }
}