:root {
  --background-start: #1d2671;
  --background-middle: #c33764;
  --background-end: #f7971e;
  --card: rgba(255, 255, 255, 0.16);
  --card-border: rgba(255, 255, 255, 0.28);
  --text-main: #ffffff;
  --text-muted: rgba(255, 255, 255, 0.72);
  --display-background: rgba(9, 12, 35, 0.35);
  --number-button: rgba(255, 255, 255, 0.16);
  --number-button-hover: rgba(255, 255, 255, 0.28);
  --operator-button: rgba(255, 199, 87, 0.95);
  --operator-text: #392100;
  --clear-button: rgba(255, 103, 112, 0.94);
  --delete-button: rgba(98, 224, 194, 0.9);
  --equals-button: #ffffff;
  --equals-text: #b42d64;
  --danger: #ffccd0;
  --shadow: 0 24px 60px rgba(17, 11, 43, 0.35);
  --radius-large: 28px;
  --radius-medium: 18px;
  --transition: 180ms ease;
}

* {
  box-sizing: border-box;
}

body {
  min-width: 320px;
  min-height: 100vh;
  margin: 0;
  color: var(--text-main);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background:
    radial-gradient(circle at 12% 18%, rgba(255, 255, 255, 0.25), transparent 25%),
    radial-gradient(circle at 88% 82%, rgba(255, 239, 186, 0.27), transparent 27%),
    linear-gradient(135deg, var(--background-start), var(--background-middle), var(--background-end));
}

button {
  font: inherit;
}

button:focus-visible {
  outline: 3px solid #ffffff;
  outline-offset: 3px;
}

.app-shell {
  display: grid;
  min-height: 100vh;
  padding: 24px 16px;
  place-items: center;
}

.calculator-layout {
  display: grid;
  width: min(100%, 1000px);
  gap: 24px;
  align-items: start;
}

.calculator-card,
.history-card {
  border: 1px solid var(--card-border);
  border-radius: var(--radius-large);
  background: var(--card);
  box-shadow: var(--shadow);
  backdrop-filter: blur(18px);
  -webkit-backdrop-filter: blur(18px);
}

.calculator-card {
  padding: 22px;
}

.calculator-header,
.history-header {
  display: flex;
  gap: 16px;
  align-items: flex-start;
  justify-content: space-between;
}

.eyebrow {
  margin: 0 0 5px;
  color: var(--text-muted);
  font-size: 0.7rem;
  font-weight: 800;
  letter-spacing: 0.12em;
}

h1,
h2 {
  margin: 0;
  letter-spacing: -0.04em;
}

h1 {
  font-size: clamp(1.55rem, 5vw, 2rem);
}

h2 {
  font-size: 1.2rem;
}

.status-dot {
  width: 12px;
  height: 12px;
  margin-top: 10px;
  border: 2px solid rgba(255, 255, 255, 0.82);
  border-radius: 50%;
  background: #67edb9;
  box-shadow: 0 0 0 6px rgba(103, 237, 185, 0.16);
}

.display-panel {
  display: flex;
  min-height: 138px;
  margin: 22px 0;
  padding: 18px;
  overflow: hidden;
  flex-direction: column;
  justify-content: flex-end;
  border: 1px solid rgba(255, 255, 255, 0.16);
  border-radius: var(--radius-medium);
  background: var(--display-background);
}

.previous-display {
  min-height: 24px;
  margin: 0 0 8px;
  overflow-wrap: anywhere;
  color: var(--text-muted);
  font-size: 0.92rem;
  text-align: right;
}

.current-display {
  display: block;
  overflow-x: auto;
  color: #ffffff;
  font-size: clamp(2rem, 9vw, 3.7rem);
  font-weight: 750;
  letter-spacing: -0.07em;
  line-height: 1.05;
  text-align: right;
  white-space: nowrap;
}

.current-display.error-display {
  color: var(--danger);
  font-size: clamp(1.25rem, 5vw, 1.75rem);
  letter-spacing: -0.03em;
  white-space: normal;
}

.calculator-keypad {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 11px;
}

.calc-button {
  min-height: 62px;
  border: 1px solid rgba(255, 255, 255, 0.18);
  border-radius: 17px;
  color: var(--text-main);
  cursor: pointer;
  font-size: 1.24rem;
  font-weight: 750;
  transition: transform var(--transition), box-shadow var(--transition), background var(--transition), filter var(--transition);
}

.calc-button:hover {
  transform: translateY(-3px);
  box-shadow: 0 10px 20px rgba(17, 11, 43, 0.2);
}

.calc-button:active {
  transform: scale(0.96);
  box-shadow: none;
}

.number-button {
  background: var(--number-button);
}

.number-button:hover {
  background: var(--number-button-hover);
}

.operator-button {
  color: var(--operator-text);
  background: var(--operator-button);
}

.operator-button:hover {
  filter: brightness(1.06);
}

.clear-button {
  background: var(--clear-button);
}

.delete-button {
  color: #073b32;
  background: var(--delete-button);
}

.equals-button {
  color: var(--equals-text);
  background: var(--equals-button);
}

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

.keyboard-help {
  display: flex;
  gap: 6px;
  margin-top: 18px;
  color: var(--text-muted);
  font-size: 0.76rem;
  justify-content: space-between;
}

.history-card {
  min-height: 270px;
  padding: 22px;
}

.history-clear-button,
.dialog-button {
  border: 0;
  border-radius: 10px;
  cursor: pointer;
  font-size: 0.8rem;
  font-weight: 750;
  transition: transform var(--transition), background var(--transition), opacity var(--transition);
}

.history-clear-button {
  padding: 9px 11px;
  color: #74233d;
  background: rgba(255, 255, 255, 0.87);
}

.history-clear-button:hover {
  transform: translateY(-2px);
  background: #ffffff;
}

.history-clear-button:disabled {
  cursor: not-allowed;
  opacity: 0.5;
}

.history-list {
  display: grid;
  gap: 10px;
  margin-top: 20px;
}

.history-item {
  display: flex;
  gap: 12px;
  align-items: center;
  justify-content: space-between;
  padding: 13px 14px;
  border: 1px solid rgba(255, 255, 255, 0.16);
  border-radius: 14px;
  background: rgba(10, 13, 38, 0.17);
}

.history-expression {
  margin: 0;
  overflow-wrap: anywhere;
  color: var(--text-muted);
  font-size: 0.84rem;
}

.history-result {
  margin: 3px 0 0;
  font-size: 1.1rem;
  font-weight: 800;
}

.empty-history {
  display: grid;
  min-height: 170px;
  padding: 20px;
  place-items: center;
  border: 1px dashed rgba(255, 255, 255, 0.32);
  border-radius: var(--radius-medium);
  color: var(--text-muted);
  text-align: center;
}

.empty-history p {
  max-width: 220px;
  margin: 0;
  line-height: 1.5;
}

.dialog-backdrop {
  position: fixed;
  z-index: 10;
  inset: 0;
  display: grid;
  padding: 20px;
  place-items: center;
  background: rgba(10, 8, 26, 0.58);
  backdrop-filter: blur(5px);
}

.dialog-backdrop[hidden] {
  display: none;
}

.dialog {
  width: min(100%, 390px);
  padding: 24px;
  border: 1px solid rgba(255, 255, 255, 0.3);
  border-radius: 22px;
  background: #fff8fb;
  color: #35223e;
  box-shadow: 0 24px 60px rgba(8, 6, 22, 0.35);
  animation: dialog-enter 180ms ease-out;
}

.dialog h2 {
  font-size: 1.35rem;
}

.dialog p {
  margin: 12px 0 22px;
  color: #6d5a72;
  line-height: 1.5;
}

.dialog-actions {
  display: flex;
  gap: 10px;
  justify-content: flex-end;
}

.dialog-button {
  padding: 11px 14px;
}

.dialog-button:hover {
  transform: translateY(-2px);
}

.cancel-dialog-button {
  color: #493649;
  background: #eee4eb;
}

.confirm-dialog-button {
  color: #ffffff;
  background: #bd365d;
}

@keyframes dialog-enter {
  from {
    opacity: 0;
    transform: translateY(8px) scale(0.97);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

@media (min-width: 760px) {
  .app-shell {
    padding: 40px 28px;
  }

  .calculator-layout {
    grid-template-columns: minmax(390px, 1fr) minmax(280px, 0.72fr);
  }

  .calculator-card,
  .history-card {
    padding: 28px;
  }

  .history-card {
    max-height: 620px;
    overflow-y: auto;
  }
}

@media (max-width: 390px) {
  .calculator-card,
  .history-card {
    padding: 17px;
    border-radius: 22px;
  }

  .calc-button {
    min-height: 56px;
    border-radius: 15px;
  }

  .keyboard-help {
    flex-direction: column;
  }
}