/* Design Tokens */
:root {
  --font-main: 'Outfit', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  /* HSL Tailored Colors */
  --bg-dark: hsl(230, 25%, 9%);
  --bg-card: hsla(230, 25%, 15%, 0.55);
  --border-card: hsla(230, 25%, 25%, 0.45);
  
  --color-text-main: hsl(0, 0%, 94%);
  --color-text-muted: hsl(230, 15%, 70%);
  --color-text-dim: hsl(230, 10%, 45%);
  
  --primary: hsl(270, 85%, 65%);
  --primary-glow: hsla(270, 85%, 65%, 0.35);
  --secondary: hsl(230, 80%, 60%);
  
  --success: hsl(145, 80%, 45%);
  --success-glow: hsla(145, 80%, 45%, 0.2);
  --error: hsl(355, 85%, 55%);
  --error-glow: hsla(355, 85%, 55%, 0.2);

  --accent-gold: hsl(45, 90%, 55%);
  
  --transition-smooth: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --shadow-premium: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
}

/* Reset */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html, body {
  overflow-x: hidden;
  width: 100%;
  position: relative;
  background-color: var(--bg-dark);
}

body {
  color: var(--color-text-main);
  font-family: var(--font-main);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

/* Glowing Backdrops */
.bg-glow-1 {
  position: absolute;
  top: -10%;
  left: -10%;
  width: 60%;
  height: 60%;
  background: radial-gradient(circle, var(--primary-glow) 0%, transparent 70%);
  pointer-events: none;
  z-index: 0;
}

.bg-glow-2 {
  position: absolute;
  bottom: -10%;
  right: -10%;
  width: 60%;
  height: 60%;
  background: radial-gradient(circle, hsla(230, 80%, 60%, 0.15) 0%, transparent 70%);
  pointer-events: none;
  z-index: 0;
}

/* Container */
.container {
  width: 100%;
  max-width: 680px;
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 20px;
  position: relative;
  z-index: 10;
}

@media(min-width: 480px) {
  .container {
    padding: 24px;
  }
}

/* Header */
header {
  text-align: center;
  margin-bottom: 4px;
}

.logo {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
}

.logo h1 {
  font-size: 2.5rem;
  font-weight: 800;
  letter-spacing: -1px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.math-symbol {
  font-size: 2.8rem;
  font-weight: 600;
  color: var(--primary);
  text-shadow: 0 0 15px var(--primary-glow);
}

.subtitle {
  font-size: 0.95rem;
  color: var(--color-text-muted);
  margin-top: 6px;
  font-weight: 300;
}

/* Stats Panel */
.stats-panel {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
}

@media(min-width: 480px) {
  .stats-panel {
    grid-template-columns: repeat(4, 1fr);
  }
}

.stat-card {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  padding: 12px;
  border-radius: 14px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  box-shadow: var(--shadow-premium);
  transition: var(--transition-smooth);
}

.stat-card:hover {
  border-color: hsla(270, 85%, 65%, 0.4);
  transform: translateY(-2px);
}

.stat-label {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--color-text-muted);
  margin-bottom: 4px;
}

.stat-val {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--color-text-main);
  font-variant-numeric: tabular-nums;
}

/* Action Bar */
.action-bar {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 10px;
}

.icon-small {
  vertical-align: middle;
}

/* Premium Select Wrapper */
.select-wrapper {
  position: relative;
  display: inline-flex;
}

.select-premium {
  appearance: none;
  -webkit-appearance: none;
  padding-right: 32px;
  cursor: pointer;
  background-image: url("data:image/svg+xml;utf8,<svg fill='white' height='20' viewBox='0 0 24 24' width='20' xmlns='http://www.w3.org/2000/svg'><path d='M7 10l5 5 5-5z'/><path d='M0 0h24v24H0z' fill='none'/></svg>");
  background-repeat: no-repeat;
  background-position-x: calc(100% - 8px);
  background-position-y: 50%;
  color: var(--color-text-main);
}

.select-premium option {
  background-color: hsl(230, 25%, 12%);
  color: var(--color-text-main);
}

/* Trainer Card */
.trainer-card {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-radius: 24px;
  padding: 16px;
  box-shadow: var(--shadow-premium);
  display: flex;
  flex-direction: column;
  gap: 16px;
  position: relative;
  overflow: hidden;
}

@media(min-width: 480px) {
  .trainer-card {
    padding: 32px;
    gap: 24px;
  }
}

.trainer-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: linear-gradient(90deg, transparent, var(--primary), var(--secondary), transparent);
}

/* Display */
.display-container {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.display-label {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--color-text-muted);
}

.pi-display {
  background: rgba(0, 0, 0, 0.2);
  border: 1px solid rgba(255, 255, 255, 0.05);
  border-radius: 12px;
  padding: 18px;
  font-family: var(--font-mono);
  font-size: 1.5rem;
  line-height: 1.7;
  letter-spacing: 1px;
  word-break: break-all;
  min-height: 72px;
  max-height: 180px;
  overflow-y: auto;
  color: var(--color-text-dim);
  transition: var(--transition-smooth);
  white-space: pre-wrap;
}

.pi-display span.correct {
  color: var(--color-text-main);
  text-shadow: 0 0 4px rgba(255, 255, 255, 0.2);
}

.pi-display span.new-digit {
  color: var(--accent-gold);
  font-weight: 700;
  text-shadow: 0 0 10px rgba(255, 190, 0, 0.5);
  animation: popIn 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.pi-display span.current-target {
  background: rgba(255, 255, 255, 0.1);
  border-bottom: 2px solid var(--primary);
  color: var(--color-text-main);
}

/* Progress Bar */
.progress-bar-container {
  width: 100%;
  height: 6px;
  background: rgba(255, 255, 255, 0.05);
  border-radius: 3px;
  overflow: hidden;
}

.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--secondary), var(--primary));
  box-shadow: 0 0 10px var(--primary-glow);
  transition: width 0.4s ease;
}

/* Input Wrapper */
.input-container {
  display: flex;
  gap: 12px;
}

#pi-input {
  flex: 1;
  background: rgba(0, 0, 0, 0.25);
  border: 2px solid var(--border-card);
  border-radius: 14px;
  padding: 16px 20px;
  font-family: var(--font-mono);
  font-size: 1.25rem;
  color: var(--color-text-main);
  outline: none;
  width: 100%;
  transition: var(--transition-smooth);
}

#pi-input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 15px var(--primary-glow);
  background: rgba(0, 0, 0, 0.4);
}

#pi-input.error {
  border-color: var(--error);
  box-shadow: 0 0 15px var(--error-glow);
  animation: shake 0.4s ease-in-out;
}

#pi-input.success-flash {
  border-color: var(--success);
  box-shadow: 0 0 15px var(--success-glow);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 24px;
  border-radius: 14px;
  font-family: var(--font-main);
  font-weight: 600;
  font-size: 1rem;
  cursor: pointer;
  border: none;
  transition: var(--transition-smooth);
}

.btn-secondary {
  background: rgba(255, 255, 255, 0.08);
  color: var(--color-text-main);
  border: 1px solid rgba(255, 255, 255, 0.1);
}

.btn-secondary:hover {
  background: rgba(255, 255, 255, 0.15);
  border-color: rgba(255, 255, 255, 0.2);
}

.btn-secondary:active {
  transform: scale(0.97);
}

.btn-small {
  padding: 10px 18px;
  font-size: 0.85rem;
  border-radius: 10px;
}

/* Feedback Msg */
.feedback-msg {
  text-align: center;
  font-size: 0.9rem;
  color: var(--color-text-muted);
  min-height: 20px;
}

.feedback-msg.error-text {
  color: var(--error);
}

.feedback-msg.success-text {
  color: var(--success);
  font-weight: 600;
}

/* Numpad */
.numpad-container {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  width: 100%;
  max-width: 320px;
  margin: 0 auto;
}

.num-key {
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: 12px;
  padding: 16px;
  font-family: var(--font-main);
  font-size: 1.35rem;
  font-weight: 600;
  color: var(--color-text-main);
  cursor: pointer;
  outline: none;
  transition: var(--transition-smooth);
}

.num-key:hover {
  background: rgba(255, 255, 255, 0.12);
  border-color: var(--primary);
}

.num-key:active {
  transform: scale(0.95);
  background: var(--primary-glow);
}

.num-key.fn-key {
  background: rgba(255, 255, 255, 0.03);
  color: var(--color-text-muted);
}

/* Heatmap Grid Styles */
.section-desc {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  margin-top: -6px;
  margin-bottom: 12px;
}

.heatmap-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 8px;
  margin: 16px 0;
  width: 100%;
}

@media(min-width: 480px) {
  .heatmap-grid {
    grid-template-columns: repeat(10, 1fr);
  }
}

.heatmap-cell {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: 10px;
  padding: 12px 6px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
  transition: var(--transition-smooth);
}

.heatmap-cell .cell-num {
  font-size: 1.15rem;
  font-weight: 700;
  font-family: var(--font-mono);
}

.heatmap-cell .cell-count {
  font-size: 0.65rem;
  color: var(--color-text-dim);
}

.btn-text-only {
  background: transparent;
  border: none;
  color: var(--color-text-dim);
  font-size: 0.8rem;
  cursor: pointer;
  transition: var(--transition-smooth);
  align-self: flex-start;
}

.btn-text-only:hover {
  color: var(--error);
  text-decoration: underline;
}

/* Reset Stats Section */
.reset-stats-container {
  display: flex;
  justify-content: center;
  margin-top: 10px;
}

.btn-danger-text {
  background: transparent;
  border: none;
  color: var(--color-text-dim);
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition-smooth);
}

.btn-danger-text:hover {
  color: var(--error);
  text-decoration: underline;
}

/* Info Card */
.info-card {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-radius: 20px;
  padding: 24px;
  box-shadow: var(--shadow-premium);
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.info-card h3 {
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--primary);
}

.info-card ul {
  list-style-type: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.info-card li {
  font-size: 0.9rem;
  line-height: 1.5;
  color: var(--color-text-muted);
  position: relative;
  padding-left: 20px;
}

.info-card li::before {
  content: "•";
  color: var(--primary);
  font-size: 1.4rem;
  position: absolute;
  left: 4px;
  top: -2px;
}

/* Modal Overlay & Modal Window */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.7);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  opacity: 0;
  transition: opacity 0.3s ease;
}

.modal-overlay.open {
  display: flex;
  opacity: 1;
}

.modal-content {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: 24px;
  padding: 32px;
  max-width: 480px;
  width: 90%;
  position: relative;
  box-shadow: var(--shadow-premium);
  display: flex;
  flex-direction: column;
  gap: 16px;
  animation: popIn 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.15);
}

.modal-content h3 {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--primary);
  border-bottom: 1px solid var(--border-card);
  padding-bottom: 8px;
}

.modal-body ul {
  list-style-type: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.modal-body li {
  font-size: 0.95rem;
  line-height: 1.6;
  color: var(--color-text-muted);
  position: relative;
  padding-left: 24px;
}

.modal-body li::before {
  content: "•";
  color: var(--primary);
  font-size: 1.5rem;
  position: absolute;
  left: 4px;
  top: -2px;
}

.modal-close {
  position: absolute;
  top: 18px;
  right: 22px;
  font-size: 2rem;
  line-height: 1;
  font-weight: 300;
  cursor: pointer;
  color: var(--color-text-dim);
  transition: var(--transition-smooth);
}

.modal-close:hover {
  color: var(--error);
}

/* Footer */
footer {
  text-align: center;
  font-size: 0.8rem;
  color: var(--color-text-dim);
  margin-top: 12px;
}

/* Animations */
@keyframes shake {
  0%, 100% { transform: translateX(0); }
  20%, 60% { transform: translateX(-6px); }
  40%, 80% { transform: translateX(6px); }
}

@keyframes popIn {
  0% { transform: scale(0.6); opacity: 0; }
  100% { transform: scale(1); opacity: 1; }
}