/* 
  Identidad Visual: "Titanio Minimalista"
  Paleta: 
    - Fondo principal: #0A0A0C (Deep Obsidian)
    - Contenedor calculadora: #141417 (Titanium Surface)
    - Acento principal: #FF9F0A (Warm Amber / Apple inspired)
    - Texto principal: #F5F5F7 (Pure Silver)
    - Texto secundario: #86868B (Muted Titanium)
    - Bordes sutiles: #26262A
    - Botón numérico: #1C1C21 (Alloy Dark)
    - Botón operador: #2C2C32
    - Botón acción: #2E1D19
  Tipografía: Inter + SF Mono
*/

:root {
  --bg-main: #0A0A0C;
  --bg-surface: #141417;
  --accent: #FF9F0A;
  --accent-hover: #E88E00;
  --text-main: #F5F5F7;
  --text-muted: #86868B;
  --border-color: #26262A;
  --btn-num: #1C1C21;
  --btn-num-hover: #2A2A30;
  --btn-op: #2C2C32;
  --btn-op-hover: #3A3A42;
  --btn-action: #2E1E1B;
  --btn-action-hover: #3E2622;
  --radius: 12px;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
}

body {
  background-color: var(--bg-main);
  color: var(--text-main);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 24px;
}

.app-container {
  width: 100%;
  max-width: 380px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.app-header {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 8px;
}

.brand-dot {
  width: 8px;
  height: 8px;
  background-color: var(--accent);
  border-radius: 50%;
  box-shadow: 0 0 10px rgba(255, 159, 10, 0.4);
}

.app-header h1 {
  font-size: 16px;
  font-weight: 500;
  letter-spacing: -0.2px;
  color: var(--text-main);
}

.mode-selector {
  display: flex;
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  padding: 3px;
  gap: 2px;
}

.mode-btn {
  flex: 1;
  background: transparent;
  border: none;
  color: var(--text-muted);
  font-size: 11px;
  font-weight: 500;
  padding: 6px;
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

.mode-btn:hover {
  color: var(--text-main);
}

.mode-btn.active {
  background-color: #222228;
  color: var(--text-main);
  font-weight: 600;
}

.calculator-card {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 20px;
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 16px;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.6), inset 0 1px 0 rgba(255, 255, 255, 0.05);
}

.display-screen {
  background-color: #0E0E10;
  border: 1px solid var(--border-color);
  border-radius: 14px;
  padding: 18px;
  text-align: right;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  min-height: 96px;
}

.history-expression {
  font-family: 'SF Mono', monospace;
  font-size: 12px;
  color: var(--text-muted);
  min-height: 18px;
  word-break: break-all;
}

.main-display {
  font-family: 'SF Mono', monospace;
  font-size: 34px;
  font-weight: 400;
  color: var(--text-main);
  word-break: break-all;
  margin-top: 4px;
  letter-spacing: -0.5px;
}

.keypad-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}

.scientific-panel {
  margin-bottom: 2px;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 14px;
}

.scientific-panel.hidden,
.history-panel.hidden {
  display: none;
}

.btn {
  background-color: var(--btn-num);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  color: var(--text-main);
  font-family: 'SF Mono', monospace;
  font-size: 15px;
  font-weight: 500;
  height: 48px;
  cursor: pointer;
  transition: background-color 0.15s ease, transform 0.08s ease, border-color 0.15s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  user-select: none;
}

.btn:hover {
  background-color: var(--btn-num-hover);
  border-color: #33333A;
}

.btn:active {
  transform: scale(0.95);
}

.btn.op {
  background-color: var(--btn-op);
  color: var(--accent);
}

.btn.op:hover {
  background-color: var(--btn-op-hover);
}

.btn.action {
  background-color: var(--btn-action);
  color: #FF453A;
}

.btn.action:hover {
  background-color: #3E2522;
}

.btn.fn {
  background-color: #18181C;
  font-size: 12px;
  color: var(--text-muted);
  border-color: #222226;
}

.btn.fn:hover {
  background-color: #222228;
  color: var(--text-main);
}

.btn.equals {
  background-color: var(--accent);
  border-color: var(--accent);
  color: #0A0A0C;
  font-weight: 600;
}

.btn.equals:hover {
  background-color: var(--accent-hover);
}

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

.history-panel {
  display: flex;
  flex-direction: column;
  gap: 12px;
  min-height: 260px;
  max-height: 260px;
}

.history-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.history-header h3 {
  font-size: 12px;
  font-weight: 500;
  color: var(--text-muted);
  letter-spacing: 0.2px;
}

.btn-clear-history {
  background: transparent;
  border: none;
  color: var(--accent);
  font-size: 11px;
  font-weight: 500;
  cursor: pointer;
}

.btn-clear-history:hover {
  text-decoration: underline;
}

.history-list {
  flex: 1;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding-right: 4px;
}

.history-item {
  background-color: #101013;
  border: 1px solid var(--border-color);
  border-radius: 10px;
  padding: 8px 12px;
  display: flex;
  flex-direction: column;
  gap: 2px;
  cursor: pointer;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

.history-item:hover {
  border-color: var(--accent);
  background-color: #16161A;
}

.history-item-expr {
  font-family: 'SF Mono', monospace;
  font-size: 11px;
  color: var(--text-muted);
}

.history-item-res {
  font-family: 'SF Mono', monospace;
  font-size: 13px;
  font-weight: 500;
  color: var(--text-main);
  text-align: right;
}

.history-empty {
  text-align: center;
  color: var(--text-muted);
  font-size: 12px;
  margin: auto 0;
}