:root {
  --color-accent: #2563eb;
  --color-accent-hover: #1d4ed8;
  --color-bg: #f5f5f7;
  --color-text: #111827;
  --color-border: #d1d5db;
  --color-error: #d92d20;
  --color-success: #039855;
}

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

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
}

main {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
}

.card {
  max-width: 420px;
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

h1 {
  font-size: clamp(24px, 4vw, 32px);
  margin: 0 0 8px;
  text-align: center;
}

form {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin: 0;
}

input[type="email"] {
  height: 48px;
  padding: 0 16px;
  border-radius: 10px;
  border: 1px solid var(--color-border);
  font: inherit;
  background: white;
}

input[type="email"]:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  border-color: transparent;
}

input[type="email"]:invalid:not(:placeholder-shown) {
  border-color: var(--color-error);
}

button[type="submit"] {
  height: 48px;
  padding: 0 24px;
  border-radius: 10px;
  border: none;
  background: var(--color-accent);
  color: white;
  font: inherit;
  font-weight: 600;
  cursor: pointer;
  transition: background 150ms ease;
}

button[type="submit"]:hover {
  background: var(--color-accent-hover);
}

button[type="submit"]:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

.message {
  min-height: 20px;
  margin: 0;
  font-size: 14px;
  text-align: center;
}

.message--error {
  color: var(--color-error);
}

.message--success {
  color: var(--color-success);
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}