body {
  font-family: Arial, sans-serif;
  background: #222;
  color: #fff;
  margin: 0;
  padding: 0;
}
.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 20px;
}
h1 {
  text-align: center;
}
.main-flex {
  display: flex;
  gap: 32px;
  flex-wrap: wrap;
}
.left-panel {
  flex: 1 1 250px;
  min-width: 220px;
  max-width: 350px;
}
.right-panel {
  flex: 1 1 350px;
  min-width: 260px;
  max-width: 500px;
  display: flex;
  flex-direction: column;
  align-items: center;
}
#question {
  font-size: 1.2rem;
  margin-bottom: 18px;
  min-height: 2.5em;
}
#feedback {
  font-weight: bold;
  margin: 12px 0;
  min-height: 2em;
}
button {
  background: #45a049;
  color: #fff;
  border: none;
  border-radius: 5px;
  padding: 10px 18px;
  font-size: 1rem;
  cursor: pointer;
  margin-top: 10px;
  width: 100%;
  max-width: 220px;
  transition: background 0.2s, color 0.2s;
}
button:disabled {
  background: #888;
  color: #ccc;
  cursor: not-allowed;
}
#sketch-holder {
  width: 100%;
  min-height: 350px;
  display: flex;
  justify-content: center;
  align-items: center;
}
canvas {
  border: 1px solid #fff;
  background: #e0e0e0;
  max-width: 100%;
  height: auto;
}
@media (max-width: 900px) {
  .main-flex {
    flex-direction: column;
    gap: 0;
  }
  .left-panel, .right-panel {
    max-width: 100%;
    min-width: 0;
  }
  #sketch-holder {
    min-height: 260px;
  }
}