:root {
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Noto Sans JP", sans-serif;
  color: #e5e7eb;
  background: #0b1020;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  background: radial-gradient(1200px 600px at 10% 10%, #1f2937, transparent),
              radial-gradient(900px 500px at 80% 20%, #111827, transparent),
              #0b1020;
}

.app-header {
  padding: 20px 16px 8px;
  text-align: center;
}

h1 { margin: 0; font-size: 24px; }
h2 { margin: 0 0 8px; font-size: 18px; }
p { margin: 8px 0; }

.muted { color: #9ca3af; }

.container {
  max-width: 720px;
  margin: 0 auto;
  padding: 12px 16px 24px;
  display: grid;
  gap: 12px;
}

.card {
  background: rgba(17, 24, 39, 0.75);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 14px;
  padding: 14px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.25);
}

.btn {
  margin-top: 10px;
  padding: 10px 12px;
  border: 0;
  border-radius: 12px;
  background: #2563eb;
  color: white;
  font-weight: 600;
  cursor: pointer;
}

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

.log {
  margin-top: 10px;
  padding: 10px;
  border-radius: 12px;
  background: rgba(0,0,0,0.3);
  min-height: 72px;
  overflow: auto;
}