:root {
  --bg: #ffffff;
  --fg: #0d1117;
  --muted: #6b7280;
  --accent: #2563eb;
  --accent-fg: #ffffff;
  --error: #b91c1c;
  --error-bg: #fef2f2;
  --border: #d1d5db;
  --code-bg: #f3f4f6;
  --radius: 10px;
  --max-width: 420px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0d1117;
    --fg: #f3f4f6;
    --muted: #9ca3af;
    --accent: #3b82f6;
    --accent-fg: #ffffff;
    --error: #fca5a5;
    --error-bg: #2a1414;
    --border: #30363d;
    --code-bg: #161b22;
  }
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.5;
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 24px 20px calc(24px + env(safe-area-inset-bottom));
  display: flex;
  flex-direction: column;
  gap: 24px;
  min-height: 100vh;
}

header h1 {
  font-size: 32px;
  font-weight: 700;
  margin: 0 0 4px 0;
  letter-spacing: -0.5px;
}

.tagline {
  color: var(--muted);
  margin: 0;
  font-size: 16px;
}

.features {
  margin: 0;
  padding-left: 20px;
  color: var(--fg);
}

.features li {
  margin-bottom: 6px;
}

form {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

label {
  font-size: 14px;
  font-weight: 500;
  color: var(--fg);
}

form label:not(:first-child) {
  margin-top: 8px;
}

input[type="text"],
input[type="email"],
input[type="password"] {
  font: inherit;
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg);
  color: var(--fg);
  width: 100%;
  -webkit-appearance: none;
  appearance: none;
}

input:focus {
  outline: 2px solid var(--accent);
  outline-offset: -1px;
  border-color: var(--accent);
}

#submit-btn {
  font: inherit;
  font-weight: 600;
  padding: 14px 20px;
  border-radius: var(--radius);
  border: none;
  cursor: pointer;
  text-align: center;
  min-height: 48px;
  background: var(--accent);
  color: var(--accent-fg);
  margin-top: 16px;
}

#submit-btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.error {
  background: var(--error-bg);
  color: var(--error);
  padding: 10px 12px;
  border-radius: var(--radius);
  font-size: 14px;
  margin: 8px 0 0;
}

.muted {
  color: var(--muted);
  font-size: 14px;
  margin: 8px 0;
}

footer {
  margin-top: auto;
  color: var(--muted);
  font-size: 14px;
  text-align: center;
}

footer p {
  margin: 4px 0;
}

footer .legal {
  font-size: 12px;
  margin-top: 12px;
}

footer a {
  color: var(--accent);
}

@media (max-width: 360px) {
  main { padding: 16px 14px; }
  header h1 { font-size: 28px; }
  .features { padding-left: 18px; }
}