/* ==========================================================================
   Variables de Tema & Estilos Globales
   ========================================================================== */

:root {
  --font-main: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono: "SF Mono", "Roboto Mono", "Fira Code", Menlo, Monaco, Consolas, monospace;

  /* Tema Oscuro (por defecto) */
  --bg-page: #090d16;
  --bg-calculator: #131b2e;
  --border-calculator: #1e293b;
  --shadow-calculator: 0 20px 40px -15px rgba(0, 0, 0, 0.7), 0 0 0 1px rgba(255, 255, 255, 0.05);

  --bg-display: #090f1d;
  --border-display: #1e293b;
  --text-expression: #94a3b8;
  --text-result: #f8fafc;
  --text-error: #f87171;

  --key-num-bg: #1e293b;
  --key-num-text: #f1f5f9;
  --key-num-hover: #29384f;
  --key-num-active: #334460;

  --key-func-bg: #152238;
  --key-func-text: #93c5fd;
  --key-func-hover: #1e3152;
  --key-func-active: #28426e;

  --key-op-bg: #1e293b;
  --key-op-text: #38bdf8;
  --key-op-hover: #2a3c57;
  --key-op-active: #374e71;

  --key-highlight-bg: #0369a1;
  --key-highlight-text: #ffffff;
  --key-highlight-hover: #0284c7;
  --key-highlight-active: #0ea5e9;

  --key-clear-bg: #881337;
  --key-clear-text: #fecdd3;
  --key-clear-hover: #9f1239;
  --key-clear-active: #be123c;

  --key-backspace-bg: #3f1d24;
  --key-backspace-text: #fda4af;
  --key-backspace-hover: #50242e;
  --key-backspace-active: #662a39;

  --key-equals-bg: #2563eb;
  --key-equals-text: #ffffff;
  --key-equals-hover: #1d4ed8;
  --key-equals-active: #1e40af;

  --bg-history: #0f172a;
  --border-history: #334155;
  --text-history-item: #cbd5e1;

  --tag-bg: #1e293b;
  --tag-text: #38bdf8;
}

[data-theme="light"] {
  --bg-page: #e2e8f0;
  --bg-calculator: #ffffff;
  --border-calculator: #cbd5e1;
  --shadow-calculator: 0 20px 35px -10px rgba(0, 0, 0, 0.15), 0 0 0 1px rgba(0, 0, 0, 0.05);

  --bg-display: #f8fafc;
  --border-display: #e2e8f0;
  --text-expression: #64748b;
  --text-result: #0f172a;
  --text-error: #dc2626;

  --key-num-bg: #f1f5f9;
  --key-num-text: #1e293b;
  --key-num-hover: #e2e8f0;
  --key-num-active: #cbd5e1;

  --key-func-bg: #e0f2fe;
  --key-func-text: #0369a1;
  --key-func-hover: #bae6fd;
  --key-func-active: #7dd3fc;

  --key-op-bg: #f8fafc;
  --key-op-text: #0284c7;
  --key-op-hover: #e2e8f0;
  --key-op-active: #cbd5e1;

  --key-highlight-bg: #0284c7;
  --key-highlight-text: #ffffff;
  --key-highlight-hover: #0369a1;
  --key-highlight-active: #075985;

  --key-clear-bg: #fee2e2;
  --key-clear-text: #b91c1c;
  --key-clear-hover: #fecaca;
  --key-clear-active: #fca5a5;

  --key-backspace-bg: #ffedd5;
  --key-backspace-text: #c2410c;
  --key-backspace-hover: #fed7aa;
  --key-backspace-active: #fdba74;

  --key-equals-bg: #0284c7;
  --key-equals-text: #ffffff;
  --key-equals-hover: #0369a1;
  --key-equals-active: #075985;

  --bg-history: #ffffff;
  --border-history: #cbd5e1;
  --text-history-item: #334155;

  --tag-bg: #e0f2fe;
  --tag-text: #0369a1;
}

/* ==========================================================================
   Reset y Estilos Base
   ========================================================================== */

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-main);
  background-color: var(--bg-page);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 16px;
  color: var(--text-result);
  transition: background-color 0.25s ease, color 0.25s ease;
  -webkit-font-smoothing: antialiased;
}

/* ==========================================================================
   Contenedor Principal
   ========================================================================== */

.calculator-container {
  width: 100%;
  max-width: 480px;
  background-color: var(--bg-calculator);
  border: 1px solid var(--border-calculator);
  border-radius: 24px;
  box-shadow: var(--shadow-calculator);
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 16px;
  position: relative;
  overflow: hidden;
  transition: background-color 0.25s ease, border-color 0.25s ease, box-shadow 0.25s ease;
}

/* ==========================================================================
   Header & Controles Superiores
   ========================================================================== */

.calculator-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
}

.header-title-group {
  display: flex;
  align-items: center;
  gap: 8px;
}

.calc-icon {
  font-family: var(--font-mono);
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--tag-text);
  background: var(--tag-bg);
  padding: 3px 8px;
  border-radius: 8px;
}

.header-title {
  font-size: 1.05rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--text-result);
}

.header-controls {
  display: flex;
  align-items: center;
  gap: 6px;
}

.badge-btn {
  background-color: var(--tag-bg);
  border: 1px solid var(--border-calculator);
  border-radius: 9999px;
  padding: 4px 10px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 0.75rem;
  font-weight: 700;
  font-family: var(--font-mono);
  color: var(--text-expression);
  transition: all 0.15s ease;
}

.badge-btn:hover {
  filter: brightness(1.1);
}

.badge-mode {
  opacity: 0.5;
  transition: opacity 0.15s ease, color 0.15s ease;
}

.badge-mode.active {
  opacity: 1;
  color: var(--tag-text);
}

.badge-divider {
  opacity: 0.3;
}

.icon-btn {
  background: var(--tag-bg);
  border: 1px solid var(--border-calculator);
  border-radius: 10px;
  width: 32px;
  height: 32px;
  display: inline-flex;
  justify-content: center;
  align-items: center;
  cursor: pointer;
  font-size: 0.9rem;
  color: var(--text-result);
  transition: all 0.15s ease;
}

.icon-btn:hover {
  filter: brightness(1.15);
  transform: translateY(-1px);
}

.icon-btn.small {
  width: 26px;
  height: 26px;
  font-size: 0.8rem;
}

.text-btn {
  background: transparent;
  border: none;
  color: var(--tag-text);
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  padding: 4px 8px;
  border-radius: 6px;
}

.text-btn:hover {
  background: var(--tag-bg);
}

/* ==========================================================================
   Panel de Historial
   ========================================================================== */

.history-panel {
  position: absolute;
  top: 195px;
  left: 16px;
  right: 16px;
  bottom: 16px;
  background-color: var(--bg-history);
  border: 1px solid var(--border-history);
  border-radius: 18px;
  z-index: 50;
  display: flex;
  flex-direction: column;
  padding: 16px;
  box-shadow: 0 15px 30px rgba(0, 0, 0, 0.5);
  animation: slideDown 0.15s cubic-bezier(0.16, 1, 0.3, 1);
}

.history-panel[hidden] {
  display: none;
}

@keyframes slideDown {
  from {
    transform: translateY(-6px);
  }
  to {
    transform: translateY(0);
  }
}

.history-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border-history);
}

.history-title {
  font-size: 0.95rem;
  font-weight: 600;
}

.history-actions {
  display: flex;
  align-items: center;
  gap: 6px;
}

.history-list {
  flex: 1;
  overflow-y: auto;
  margin-top: 12px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding-right: 4px;
}

.history-empty {
  text-align: center;
  color: var(--text-expression);
  font-size: 0.85rem;
  margin-top: 40px;
}

.history-item {
  background: var(--key-num-bg);
  border: 1px solid var(--border-calculator);
  border-radius: 12px;
  padding: 10px 12px;
  cursor: pointer;
  text-align: right;
  display: flex;
  flex-direction: column;
  gap: 4px;
  transition: all 0.15s ease;
}

.history-item:hover {
  border-color: var(--tag-text);
  transform: translateX(-2px);
}

.history-item-expr {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--text-expression);
  word-break: break-all;
}

.history-item-res {
  font-family: var(--font-mono);
  font-size: 1rem;
  font-weight: 600;
  color: var(--tag-text);
}

/* ==========================================================================
   Pantalla (Display)
   ========================================================================== */

.display-container {
  background-color: var(--bg-display);
  border: 1px solid var(--border-display);
  border-radius: 18px;
  padding: 16px 18px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  min-height: 110px;
  text-align: right;
  word-break: break-all;
  overflow: hidden;
  transition: background-color 0.25s ease, border-color 0.25s ease;
}

.display-meta {
  display: flex;
  justify-content: flex-start;
  align-items: center;
  gap: 6px;
  min-height: 18px;
}

.meta-tag {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--tag-text);
  background: var(--tag-bg);
  padding: 2px 6px;
  border-radius: 4px;
}

.meta-tag.hidden {
  display: none;
}

.expression-line {
  font-family: var(--font-mono);
  font-size: 1rem;
  color: var(--text-expression);
  min-height: 24px;
  line-height: 1.4;
  overflow-x: auto;
  white-space: nowrap;
  scrollbar-width: thin;
}

.result-line {
  font-family: var(--font-mono);
  font-size: 2rem;
  font-weight: 600;
  color: var(--text-result);
  min-height: 44px;
  display: flex;
  justify-content: flex-end;
  align-items: center;
  overflow-x: auto;
  white-space: nowrap;
  scrollbar-width: none;
  transition: color 0.15s ease, font-size 0.15s ease;
}

.result-line.error {
  color: var(--text-error);
  font-size: 1.15rem;
  font-weight: 500;
  white-space: normal;
  text-align: right;
}

/* ==========================================================================
   Teclado (Keypad Grid)
   ========================================================================== */

.keypad-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 8px;
}

.key {
  font-family: var(--font-main);
  font-size: 1rem;
  font-weight: 600;
  border: none;
  border-radius: 12px;
  min-height: 48px;
  display: inline-flex;
  justify-content: center;
  align-items: center;
  cursor: pointer;
  user-select: none;
  touch-action: manipulation;
  transition: background-color 0.12s ease, transform 0.08s ease, filter 0.12s ease;
}

.key:hover {
  filter: brightness(1.1);
}

.key:active, .key.is-pressed {
  transform: scale(0.95);
  filter: brightness(0.9);
}

/* Tipos de Teclas */
.num-key {
  background-color: var(--key-num-bg);
  color: var(--key-num-text);
  font-family: var(--font-mono);
  font-size: 1.15rem;
}

.func-key, .const-key {
  background-color: var(--key-func-bg);
  color: var(--key-func-text);
  font-size: 0.9rem;
}

.op-key, .paren-key, .action-key {
  background-color: var(--key-op-bg);
  color: var(--key-op-text);
  font-size: 1.05rem;
}

.highlight-op {
  background-color: var(--key-highlight-bg);
  color: var(--key-highlight-text);
}

.clear-key {
  background-color: var(--key-clear-bg);
  color: var(--key-clear-text);
}

.backspace-key {
  background-color: var(--key-backspace-bg);
  color: var(--key-backspace-text);
}

.equals-key {
  background-color: var(--key-equals-bg);
  color: var(--key-equals-text);
  font-size: 1.4rem;
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

.equals-key:hover {
  filter: brightness(1.12);
}

/* Spans para la última fila */
.span-3 {
  grid-column: span 3;
}

.span-2 {
  grid-column: span 2;
}

/* ==========================================================================
   Responsive (Móviles y Pantallas Pequeñas)
   ========================================================================== */

@media (max-width: 440px) {
  body {
    padding: 8px;
  }

  .calculator-container {
    padding: 14px 12px;
    border-radius: 20px;
    gap: 12px;
  }

  .keypad-grid {
    gap: 6px;
  }

  .key {
    min-height: 44px;
    font-size: 0.95rem;
    border-radius: 10px;
  }

  .num-key {
    font-size: 1.05rem;
  }

  .func-key, .const-key {
    font-size: 0.8rem;
  }

  .result-line {
    font-size: 1.7rem;
  }

  .result-line.error {
    font-size: 1rem;
  }
}