:root {
  --bg: #f6f8fb;
  --card-bg: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --border: #d1d5db;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 24px;
}

.card {
  width: 100%;
  max-width: 420px;
  background: var(--card-bg);
  border-radius: 16px;
  box-shadow: var(--shadow);
  padding: 32px 24px;
}

h1 {
  margin: 0 0 8px;
  font-size: 28px;
  text-align: center;
}

p.subtitle {
  margin: 0 0 28px;
  text-align: center;
  color: var(--muted);
  font-size: 15px;
}

.provider-list {
  display: grid;
  gap: 12px;
}

.provider-btn {
  width: 100%;
  min-height: 48px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: #fff;
  color: #111827;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  padding: 0 16px;
  transition: transform 0.05s ease, box-shadow 0.15s ease, background 0.15s ease;
}

.provider-btn:hover {
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.08);
}

.provider-btn:active {
  transform: translateY(1px);
}

.provider-btn:focus-visible {
  outline: 3px solid #93c5fd;
  outline-offset: 2px;
}

.provider-btn.google {
  background: #fff;
  color: #3c4043;
}

.provider-btn.microsoft {
  background: #fff;
  color: #111827;
}

.provider-btn.apple {
  background: #000;
  color: #fff;
  border-color: #000;
}

.icon {
  width: 20px;
  height: 20px;
  display: inline-block;
  flex: 0 0 20px;
}

.footer-note {
  margin-top: 20px;
  text-align: center;
  font-size: 13px;
  color: var(--muted);
  line-height: 1.4;
}