:root {
  color-scheme: dark;
  --bg-top: #20130f;
  --bg-bottom: #090909;
  --card-top: rgba(33, 22, 16, 0.95);
  --card-bottom: rgba(10, 10, 10, 0.98);
  --border: rgba(255, 255, 255, 0.08);
  --banner-text: #fff7ed;
  --text-main: #fff7ed;
  --text-muted: rgba(255, 247, 237, 0.76);
  --display-bg: rgba(255, 255, 255, 0.04);
  --key-bg: rgba(255, 255, 255, 0.06);
  --key-utility: rgba(255, 255, 255, 0.14);
  --key-operator: #fb923c;
  --key-equals: #ea580c;
  --shadow: 0 24px 64px rgba(0, 0, 0, 0.45);
  --banner-checking: linear-gradient(135deg, #475569, #1e293b);
  --banner-online: linear-gradient(135deg, #b91c1c, #7f1d1d);
  --banner-offline: linear-gradient(135deg, #15803d, #14532d);
  --font-ui: "Avenir Next", "Avenir", "Trebuchet MS", "Segoe UI", sans-serif;
  --font-display: "Avenir Next Condensed", "Arial Narrow", "Avenir Next",
    sans-serif;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
  font-family: var(--font-ui);
  background:
    radial-gradient(circle at top, rgba(249, 115, 22, 0.24), transparent 38%),
    linear-gradient(180deg, var(--bg-top), var(--bg-bottom));
  color: var(--text-main);
}

body {
  min-height: 100vh;
  min-height: 100dvh;
}

button {
  font: inherit;
}

.app-shell {
  width: min(100%, 36rem);
  margin: 0 auto;
  padding:
    calc(env(safe-area-inset-top, 0px) + 1rem)
    1rem
    calc(env(safe-area-inset-bottom, 0px) + 1.25rem);
}

.network-banner {
  padding: 1rem 1rem 0.95rem;
  border-radius: 1.5rem;
  color: var(--banner-text);
  box-shadow: var(--shadow);
  border: 1px solid rgba(255, 255, 255, 0.1);
}

.network-banner.state-checking {
  background: var(--banner-checking);
}

.network-banner.state-online {
  background: var(--banner-online);
}

.network-banner.state-offline {
  background: var(--banner-offline);
}

.banner-label,
.banner-value,
.banner-caption {
  margin: 0;
}

.banner-label {
  text-transform: uppercase;
  letter-spacing: 0.18em;
  font-size: 0.72rem;
  opacity: 0.78;
}

.banner-value {
  margin-top: 0.3rem;
  font-family: var(--font-display);
  font-size: clamp(1.45rem, 6vw, 2.1rem);
  font-weight: 700;
  letter-spacing: 0.03em;
}

.banner-caption {
  margin-top: 0.2rem;
  font-size: 0.92rem;
  opacity: 0.88;
}

.calculator-card {
  margin-top: 1rem;
  padding: 1.15rem;
  border-radius: 2rem;
  background: linear-gradient(180deg, var(--card-top), var(--card-bottom));
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
  backdrop-filter: blur(14px);
}

.hero {
  margin-bottom: 1rem;
}

.eyebrow {
  margin: 0;
  color: #fdba74;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  font-size: 0.72rem;
}

.hero h1 {
  margin: 0.3rem 0 0;
  font-family: var(--font-display);
  font-size: clamp(2rem, 8vw, 3.4rem);
  line-height: 0.95;
  letter-spacing: 0.02em;
}

.hero-copy {
  margin: 0.55rem 0 0;
  color: var(--text-muted);
  font-size: 0.98rem;
  line-height: 1.45;
}

.display-wrap {
  padding: 1rem;
  border-radius: 1.5rem;
  background: var(--display-bg);
  border: 1px solid var(--border);
}

.expression {
  min-height: 1.5rem;
  color: var(--text-muted);
  font-size: 0.95rem;
  letter-spacing: 0.04em;
  text-align: right;
}

.display {
  min-height: 4.5rem;
  margin-top: 0.35rem;
  font-family: var(--font-display);
  font-size: clamp(3rem, 13vw, 4.8rem);
  line-height: 1;
  text-align: right;
  word-break: break-all;
}

.keypad {
  margin-top: 1rem;
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 0.8rem;
}

.key {
  min-height: 4.75rem;
  border: 0;
  border-radius: 1.45rem;
  background: var(--key-bg);
  color: var(--text-main);
  font-family: var(--font-display);
  font-size: 2rem;
  font-weight: 700;
  touch-action: manipulation;
  box-shadow:
    inset 0 1px 0 rgba(255, 255, 255, 0.06),
    0 16px 32px rgba(0, 0, 0, 0.26);
}

.key:active {
  transform: scale(0.98);
}

.key-utility {
  background: var(--key-utility);
}

.key-operator {
  background: linear-gradient(180deg, #fb923c, #ea580c);
}

.key-equals {
  background: linear-gradient(180deg, #f97316, #c2410c);
}

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

@media (min-width: 48rem) {
  .app-shell {
    width: min(100%, 42rem);
    padding-top: 1.5rem;
  }

  .calculator-card {
    padding: 1.4rem;
  }

  .key {
    min-height: 5.2rem;
  }
}