:root { --bg: #1f2430; --panel: #2b303b; --text: #e6e6e6; --accent: #6c9; --bad: #e06c75; }
* { box-sizing: border-box; }
body { margin: 0; font-family: system-ui, sans-serif; background: var(--bg); color: var(--text); }
header { padding: 1rem 1.5rem; background: var(--panel); }
header h1 { margin: 0; font-size: 1.4rem; }
main { max-width: 560px; margin: 0 auto; padding: 1.5rem; }
#opening-list { list-style: none; padding: 0; }
#opening-list li button {
  width: 100%; text-align: left; padding: 1rem; margin: 0.5rem 0; cursor: pointer;
  background: var(--panel); color: var(--text); border: 1px solid #3a4150; border-radius: 8px; font-size: 1.05rem;
}
#opening-list li button:hover { border-color: var(--accent); }
#board { width: 100%; max-width: 480px; margin: 1rem auto; }
#instruction { font-size: 1.1rem; min-height: 1.5em; }
#feedback { min-height: 1.5em; font-weight: 600; }
#feedback.bad { color: var(--bad); }
#feedback.good { color: var(--accent); }
#back-btn { background: none; border: none; color: var(--accent); cursor: pointer; font-size: 0.95rem; padding: 0; }
#reset-btn {
  background: var(--bad); color: #1f2430; border: none; border-radius: 8px;
  padding: 0.6rem 1rem; font-size: 1rem; font-weight: 600; cursor: pointer;
}
#reset-btn:hover { filter: brightness(1.1); }
#line-counter { margin-top: 1.25rem; text-align: center; color: #9aa4b5; font-size: 0.95rem; }

.modal-overlay {
  position: fixed; inset: 0; background: rgba(0, 0, 0, 0.6);
  display: flex; align-items: center; justify-content: center; z-index: 10;
}
.modal-box {
  background: var(--panel); border: 1px solid #3a4150; border-radius: 12px;
  padding: 2rem; max-width: 320px; text-align: center;
}
.modal-box p { font-size: 1.2rem; margin: 0 0 1.25rem; }
.modal-box button {
  background: var(--accent); color: #1f2430; border: none; border-radius: 8px;
  padding: 0.7rem 1.4rem; font-size: 1.05rem; font-weight: 600; cursor: pointer;
}
.modal-box button:hover { filter: brightness(1.1); }
[hidden] { display: none !important; }