:root {
  --bg: #000000;
  --panel: #050505;
  --card: #000000;
  --digit: #050505;
  --digit-active: #111111;
  --action: #050505;
  --action-active: #111111;
  --line: rgba(255, 255, 255, 0.14);
  --line-hot: rgba(255, 255, 255, 0.32);
  --title: #e9c35b;
  --text: #e8e8e8;
  --text-dim: #8b8b8b;
  --good: #70c6a9;
  --warn: #d4186c;
  --info: #b9b9b9;
  --shadow: rgba(0, 0, 0, 0.38);
  --display-font: "Avenir Next", "Helvetica Neue", "Segoe UI", sans-serif;
  color-scheme: dark;
  font-family: "Courier New", Courier, monospace;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
  background: var(--bg);
  color: var(--text);
}

body {
  min-height: 100vh;
}

button,
input,
textarea,
select {
  font: inherit;
}

.app-shell {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
  padding: 20px 14px 28px;
}

.game-shell {
  width: min(100%, 520px);
  min-height: min(92vh, 760px);
  background: #000;
  border: 1px solid var(--line);
  box-shadow: none;
  padding: 12px;
  display: flex;
  flex-direction: column;
}

.topbar {
  padding-bottom: 10px;
  border-bottom: 1px solid var(--line);
}

.topbar h1 {
  margin: 0;
  font-size: 0.95rem;
  letter-spacing: 0.08em;
  color: var(--text-dim);
}

.meta-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 6px 18px;
  margin-top: 12px;
  font-size: 0.86rem;
}

.meta-grid p {
  margin: 0;
}

#bestLabel {
  text-align: right;
  color: var(--text-dim);
}

#accuracyLabel {
  text-align: right;
  color: var(--info);
}

.screen {
  display: none;
  flex: 1;
  margin-top: 10px;
}

.screen.active {
  display: flex;
  flex-direction: column;
  flex: 1;
}

.panel {
  border: 1px solid var(--line);
}

.problem-card {
  background: #000;
  padding: 20px 14px 10px;
}

.problem-text {
  min-height: 120px;
  display: grid;
  place-items: center;
  text-align: center;
  font-family: var(--display-font);
  font-size: clamp(2.1rem, 5.6vw, 3rem);
  line-height: 1;
  letter-spacing: 0.02em;
  font-weight: 400;
  font-variant-numeric: lining-nums tabular-nums;
  font-feature-settings: "lnum" 1, "tnum" 1;
  -webkit-font-smoothing: antialiased;
  text-rendering: geometricPrecision;
  color: var(--text);
  text-shadow: none;
}

.timer-track {
  margin-top: 10px;
  height: 10px;
  border: 1px solid rgba(255, 255, 255, 0.08);
  background: #050505;
  overflow: hidden;
}

.timer-bar {
  --timer-fill: #5f5f5f;
  height: 100%;
  width: 100%;
  display: flex;
  gap: 2px;
  padding: 1px;
}

.timer-block {
  flex: 1;
  background: transparent;
  opacity: 0.18;
  transition: opacity 80ms linear, background-color 80ms linear;
}

.timer-block.active {
  background: var(--timer-fill);
  opacity: 1;
}

.status-row {
  margin-top: 8px;
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 8px;
  align-items: center;
  font-size: 0.72rem;
}

.status-row p {
  margin: 0;
}

#instructionText {
  color: var(--text);
}

#statusText {
  color: var(--text-dim);
  text-align: right;
}

.keypad {
  flex: 1;
  margin-top: 6px;
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  grid-auto-rows: minmax(92px, 1fr);
  gap: 1px;
  background: var(--line);
  padding: 1px;
}

.key,
.page-links a {
  border: 1px solid transparent;
  background: var(--digit);
  color: var(--text);
  font-weight: 500;
  letter-spacing: 0.04em;
  box-shadow: none;
}

.key {
  appearance: none;
  border-radius: 0;
  cursor: pointer;
  transition: background 120ms ease, border-color 120ms ease, transform 120ms ease;
}

.key:hover,
.key:focus-visible {
  border-color: var(--line-hot);
  outline: none;
}

.key:active {
  transform: translateY(1px);
}

.key.digit {
  font-family: var(--display-font);
  font-size: clamp(2rem, 7.8vw, 3rem);
  color: #d7d7d7;
  font-weight: 400;
  letter-spacing: 0;
  font-variant-numeric: lining-nums tabular-nums;
  font-feature-settings: "lnum" 1, "tnum" 1;
  -webkit-font-smoothing: antialiased;
  text-rendering: geometricPrecision;
}

.key.action {
  background: var(--action);
  font-family: var(--display-font);
  font-size: clamp(1rem, 3vw, 1.25rem);
  color: #cfcfcf;
  font-weight: 400;
  letter-spacing: 0.02em;
  -webkit-font-smoothing: antialiased;
}

.key.digit:hover,
.key.digit:focus-visible {
  background: var(--digit-active);
}

.key.action:hover,
.key.action:focus-visible {
  background: var(--action-active);
}

.result-screen {
  justify-content: flex-start;
}

.result-card {
  background: var(--card);
  padding: 18px;
}

.result-card h2,
.result-card p {
  margin: 0;
}

.result-card h2 {
  font-size: 1rem;
}

#resultScore,
#resultAccuracy {
  margin-top: 16px;
  font-size: 0.92rem;
}

#resultAccuracy {
  color: var(--info);
}

.result-message {
  margin-top: 20px !important;
  font-size: 1rem;
  color: var(--good);
}

.result-hint {
  margin-top: 20px !important;
  color: var(--text-dim);
  font-size: 0.8rem;
}

.result-actions {
  margin-top: 18px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.page-links {
  width: min(100%, 520px);
  text-align: right;
  font-size: 0.84rem;
}

.page-links a {
  display: inline-block;
  text-decoration: none;
  padding: 8px 10px;
}

@media (max-width: 420px) {
  .app-shell {
    padding: 10px 8px 18px;
  }

  .game-shell {
    min-height: min(94vh, 760px);
    padding: 8px;
  }

  .meta-grid {
    font-size: 0.78rem;
    gap: 5px 10px;
  }

  .problem-text {
    min-height: 96px;
    font-size: clamp(1.7rem, 8vw, 2.35rem);
  }

  .keypad {
    grid-auto-rows: minmax(82px, 1fr);
    gap: 1px;
    padding: 1px;
  }

  .key.digit {
    font-size: clamp(1.9rem, 8.6vw, 2.45rem);
  }
}