:root {
  --bg: #f4f6fb;
  --surface: #ffffff;
  --border: #e4e8f0;
  --text: #16181f;
  --text-muted: #6b7280;
  --primary: #2f6bff;
  --primary-hover: #2557d6;
  --primary-contrast: #ffffff;
  --danger: #d64545;
  --danger-bg: #fdeeee;
  --ok: #1fa971;
  --warn: #e8a33d;
  --radius: 14px;
  --radius-sm: 10px;
  --shadow: 0 1px 2px rgba(16, 24, 40, 0.04), 0 8px 24px rgba(16, 24, 40, 0.06);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
}

body {
  font-size: 15px;
  line-height: 1.55;
}

.page {
  max-width: 560px;
  margin: 0 auto;
  padding: 28px 20px 56px;
}

.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 4px 2px 28px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
}

.brand__name {
  font-weight: 700;
  font-size: 18px;
  letter-spacing: -0.01em;
}

.header__tag {
  font-size: 12.5px;
  color: var(--text-muted);
  background: var(--surface);
  border: 1px solid var(--border);
  padding: 4px 10px;
  border-radius: 999px;
}

.intro h1 {
  font-size: 24px;
  font-weight: 700;
  letter-spacing: -0.015em;
  margin: 0 0 10px;
}

.intro p {
  color: var(--text-muted);
  margin: 0 0 22px;
}

.intro code {
  background: var(--border);
  padding: 1px 6px;
  border-radius: 5px;
  font-size: 13px;
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
  margin-bottom: 24px;
}

.field { margin-bottom: 18px; }
.field label {
  display: block;
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 7px;
  color: var(--text);
}

.field input {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 11px 13px;
  font-size: 15px;
  background: #fbfcfe;
  color: var(--text);
  outline: none;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.field input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(47, 107, 255, 0.12);
  background: var(--surface);
}

.input-prefix {
  display: flex;
  align-items: stretch;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: #fbfcfe;
  overflow: hidden;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}
.input-prefix:focus-within {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(47, 107, 255, 0.12);
  background: var(--surface);
}
.input-prefix span {
  display: flex;
  align-items: center;
  padding: 0 4px 0 13px;
  color: var(--text-muted);
  font-size: 15px;
}
.input-prefix input {
  border: none;
  background: transparent;
  box-shadow: none !important;
}

.hint {
  display: block;
  margin-top: 6px;
  font-size: 12.5px;
  color: var(--text-muted);
}

.btn {
  width: 100%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  border: none;
  border-radius: var(--radius-sm);
  padding: 12px 16px;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: background-color 0.15s ease, transform 0.05s ease, opacity 0.15s ease;
}
.btn:active { transform: translateY(1px); }
.btn:disabled { opacity: 0.55; cursor: not-allowed; }

.btn--primary {
  background: var(--primary);
  color: var(--primary-contrast);
}
.btn--primary:hover:not(:disabled) { background: var(--primary-hover); }

.btn--ghost {
  background: transparent;
  color: var(--primary);
  border: 1px solid var(--border);
}
.btn--ghost:hover { background: #f0f4ff; }

.spinner {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  border: 2px solid rgba(255, 255, 255, 0.4);
  border-top-color: #fff;
  animation: spin 0.7s linear infinite;
}
.spinner--inline {
  border: 2px solid rgba(47, 107, 255, 0.25);
  border-top-color: var(--primary);
  flex: none;
}
@keyframes spin { to { transform: rotate(360deg); } }

.form-error {
  margin: 14px 0 0;
  padding: 10px 12px;
  border-radius: 8px;
  background: var(--danger-bg);
  color: var(--danger);
  font-size: 13.5px;
}

.result { text-align: left; }
.result__icon {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 14px;
}
.result h2 {
  font-size: 19px;
  margin: 0 0 8px;
  letter-spacing: -0.01em;
}
.result p { margin: 0 0 10px; }
.muted { color: var(--text-muted); }

.tariffs {
  display: grid;
  gap: 10px;
  margin: 18px 0 18px;
}
.tariff {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 13px 15px;
  cursor: pointer;
  background: #fbfcfe;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}
.tariff:hover { border-color: #c7d3ff; }
.tariff.is-selected {
  border-color: var(--primary);
  background: #f2f6ff;
}
.tariff__name { font-weight: 600; }
.tariff__price { font-weight: 700; color: var(--primary); }
.tariff__badge {
  font-size: 11.5px;
  font-weight: 700;
  color: var(--ok);
  background: #e8f8f1;
  padding: 2px 8px;
  border-radius: 999px;
  margin-left: 8px;
}

.pay-waiting {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-top: 16px;
  padding: 12px 14px;
  background: #f2f6ff;
  border-radius: var(--radius-sm);
  font-size: 13.5px;
  color: var(--text-muted);
}
.pay-fallback {
  margin-top: 12px;
  font-size: 13.5px;
  color: var(--text-muted);
}

.howto {
  margin-top: 8px;
}
.howto h2 {
  font-size: 16px;
  margin: 0 0 10px;
}
.howto ol {
  margin: 0;
  padding-left: 20px;
  color: var(--text-muted);
}
.howto li { margin-bottom: 6px; }
.howto code {
  background: var(--border);
  padding: 1px 6px;
  border-radius: 5px;
  font-size: 13px;
  color: var(--text);
}

.footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 40px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
  font-size: 13px;
  color: var(--text-muted);
}
.footer a {
  color: var(--primary);
  text-decoration: none;
}
.footer a:hover { text-decoration: underline; }

@media (max-width: 420px) {
  .page { padding: 20px 14px 40px; }
  .card { padding: 18px; }
}