/* ===== Base Reset & Theme ===== */
* {
  box-sizing: border-box;
}
:root {
  --bg: #0f172a; /* slate-900 */
  --card: #111827; /* gray-900 */
  --muted: #94a3b8; /* slate-400 */
  --text: #e5e7eb; /* gray-200 */
  --accent: #22d3ee; /* cyan-400 */
  --accent-2: #06b6d4; /* cyan-500 */
  --danger: #f43f5e; /* rose-500 */
  --success: #22c55e; /* green-500 */
  --ring: rgba(34, 211, 238, 0.35);
  --radius: 16px;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.45);
}

html,
body {
  height: 100dvh;
}

body {
  margin: 0;
  background: radial-gradient(1200px 800px at 10% 10%, #0b1220 0%, var(--bg) 60%),
    radial-gradient(1200px 800px at 90% 90%, #0b1220 0%, var(--bg) 60%);
  color: var(--text);
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  display: grid;
  place-items: center;
  padding: 24px;
}

/* ===== Layout ===== */
main {
  width: 100%;
  max-width: 560px;
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.02), rgba(255, 255, 255, 0));
  border: 1px solid rgba(255, 255, 255, 0.06);
  backdrop-filter: blur(6px);
  box-shadow: var(--shadow);
  border-radius: var(--radius);
  padding: 28px;
}

h1 {
  font-family: "Castoro Titling", ui-serif, Georgia, "Times New Roman", serif;
  letter-spacing: 0.03em;
  line-height: 1.15;
  margin: 0 0 18px;
  color: #f8fafc;
  text-align: center;
  text-shadow: 0 1px 0 rgba(0, 0, 0, 0.3);
}

.form fieldset {
  margin: 0;
  padding: 16px;
  border: 1px dashed rgba(255, 255, 255, 0.08);
  border-radius: calc(var(--radius) - 6px);
  display: grid;
  gap: 10px;
}

label {
  color: var(--muted);
  font-size: 0.95rem;
}

input[type="number"] {
  width: 100%;
  appearance: textfield;
  border: 1px solid rgba(255, 255, 255, 0.1);
  background: rgba(17, 24, 39, 0.6);
  color: var(--text);
  border-radius: 12px;
  padding: 12px 14px;
  font-size: 1rem;
  outline: none;
  transition: all 0.3s ease;
}
input[type="number"]::placeholder {
  color: #9aa6b2;
}
input[type="number"]:hover {
  border-color: rgba(255, 255, 255, 0.2);
}
input[type="number"]:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 6px var(--ring);
  background: rgba(17, 24, 39, 0.8);
}

input[type="number"]::-webkit-outer-spin-button,
input[type="number"]::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

#convert-btn {
  margin: 19px 0;
  border: none;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  color: #001219;
  font-weight: 700;
  padding: 10px 16px;
  border-radius: 12px;
  cursor: pointer;
  transition: transform 0.06s ease, filter 0.2s ease, box-shadow 0.2s ease;
  box-shadow: 0 6px 18px rgba(6, 182, 212, 0.35);
}
#convert-btn:hover {
  filter: brightness(1.06);
}
#convert-btn:active {
  transform: translateY(1px) scale(0.99);
}
#convert-btn:focus-visible {
  outline: 0;
  box-shadow: 0 0 0 6px var(--ring), 0 6px 18px rgba(6, 182, 212, 0.45);
}

/* ===== Output ===== */
.output {
  margin-top: 16px;
  padding: 14px 16px;
  border-radius: 12px;
  background: rgba(34, 197, 94, 0.08); /* subtle success bg by default */
  border: 1px solid rgba(255, 255, 255, 0.08);
  font-size: 1.05rem;
  line-height: 1.35;
  word-break: break-word;
  opacity: 1;
  transform: translateY(0);
  transition: all 0.3s ease;
}

/* JS */
.hidden {
  opacity: 0 !important;
  transform: translateY(-6px) !important;
  pointer-events: none;
}

.output.error {
  background: rgba(244, 63, 94, 0.1);
  border-color: rgba(244, 63, 94, 0.35);
}
.output.ok {
  background: rgba(34, 197, 94, 0.1);
  border-color: rgba(34, 197, 94, 0.35);
}

/* ===== Small screens ===== */
@media (max-width: 480px) {
  main {
    padding: 22px;
  }
  .form fieldset {
    padding: 14px;
  }
  #convert-btn {
    width: 100%;
    justify-self: stretch;
    text-align: center;
  }
}

/* ===== Nice subtle focus visible for all controls ===== */
:where(button, input):focus-visible {
  outline: none;
  box-shadow: 0 0 0 6px var(--ring);
}