*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --bg: #0f172a;
  --text: #e2e8f0;
  --heading: #f8fafc;
  --subtitle: #94a3b8;
  --card-bg: #1e293b;
  --card-border: #334155;
  --card-border-hover: #475569;
  --card-label: #94a3b8;
  --field-label: #64748b;
  --input-bg: #0f172a;
  --input-border: #334155;
  --input-text: #f1f5f9;
  --arrow: #475569;
  --focus-ring: rgba(99, 102, 241, 0.15);
  --focus-border: #6366f1;
  --toggle-bg: #334155;
  --toggle-hover: #475569;
  --toggle-text: #e2e8f0;
}

[data-theme="light"] {
  --bg: #f1f5f9;
  --text: #1e293b;
  --heading: #0f172a;
  --subtitle: #64748b;
  --card-bg: #ffffff;
  --card-border: #cbd5e1;
  --card-border-hover: #94a3b8;
  --card-label: #64748b;
  --field-label: #475569;
  --input-bg: #f8fafc;
  --input-border: #cbd5e1;
  --input-text: #0f172a;
  --arrow: #94a3b8;
  --focus-ring: rgba(99, 102, 241, 0.2);
  --focus-border: #6366f1;
  --toggle-bg: #cbd5e1;
  --toggle-hover: #94a3b8;
  --toggle-text: #1e293b;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  padding: 2rem 1rem;
  transition: background 0.3s, color 0.3s;
}

.container {
  max-width: 480px;
  width: 100%;
}

.header-row {
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
}

h1 {
  font-size: 1.75rem;
  font-weight: 700;
  text-align: center;
  color: var(--heading);
}

.theme-toggle {
  position: absolute;
  right: 0;
  background: var(--toggle-bg);
  border: 1px solid var(--card-border);
  border-radius: 8px;
  color: var(--toggle-text);
  cursor: pointer;
  width: 38px;
  height: 38px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  transition: background 0.2s, border-color 0.2s;
  line-height: 1;
}

.theme-toggle:hover {
  background: var(--toggle-hover);
  border-color: var(--card-border-hover);
}

.icon-sun { display: none; }
.icon-moon { display: inline; }

[data-theme="light"] .icon-sun { display: inline; }
[data-theme="light"] .icon-moon { display: none; }

.subtitle {
  text-align: center;
  color: var(--subtitle);
  font-size: 0.875rem;
  margin: 0.25rem 0 1.5rem;
}

.card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 12px;
  padding: 1.25rem 1.5rem;
  margin-bottom: 1rem;
  transition: border-color 0.2s, background 0.3s;
}

.card:hover {
  border-color: var(--card-border-hover);
}

.card h2 {
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--card-label);
  margin-bottom: 0.75rem;
}

.fields {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.field {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.field label {
  font-size: 0.75rem;
  color: var(--field-label);
  font-weight: 500;
}

.field input {
  width: 100%;
  padding: 0.6rem 0.75rem;
  font-size: 1.1rem;
  font-family: inherit;
  background: var(--input-bg);
  border: 1px solid var(--input-border);
  border-radius: 8px;
  color: var(--input-text);
  outline: none;
  transition: border-color 0.2s, box-shadow 0.2s, background 0.3s, color 0.3s;
  -moz-appearance: textfield;
}

.field input::-webkit-outer-spin-button,
.field input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

.field input:focus {
  border-color: var(--focus-border);
  box-shadow: 0 0 0 3px var(--focus-ring);
}

.arrow {
  font-size: 1.25rem;
  color: var(--arrow);
  margin-top: 1.1rem;
  flex-shrink: 0;
}

@media (max-width: 400px) {
  .fields {
    flex-direction: column;
    gap: 0.5rem;
  }
  .arrow {
    margin-top: 0;
    transform: rotate(90deg);
  }
}