body {
  font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, Roboto, sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
  background-color: #f0f2f5;
  transition: background-color 0.3s, color 0.3s;
}

body.dark-mode {
  background-color: #1a1a1a;
  color: #ffffff;
}

.container {
  text-align: center;
  background-color: white;
  padding: 3rem;
  border-radius: 20px;
  box-shadow: 0 10px 25px rgba(0,0,0,0.1);
  transition: background-color 0.3s, box-shadow 0.3s;
  position: relative;
}

body.dark-mode .container {
  background-color: #2d2d2d;
  box-shadow: 0 10px 25px rgba(0,0,0,0.5);
}

h1 {
  color: #333;
  margin-bottom: 2rem;
  transition: color 0.3s;
}

body.dark-mode h1 {
  color: #ffffff;
}

.theme-btn {
  position: absolute;
  top: 1rem;
  right: 1rem;
  padding: 0.5rem 1rem;
  font-size: 0.8rem;
  background-color: #eee;
  color: #333;
  border-radius: 5px;
  border: none;
  cursor: pointer;
  transition: background-color 0.3s, color 0.3s;
}

body.dark-mode .theme-btn {
  background-color: #444;
  color: #fff;
}

.numbers-container {
  display: flex;
  gap: 15px;
  justify-content: center;
  margin-bottom: 2rem;
  min-height: 60px;
}

.ball {
  width: 60px;
  height: 60px;
  border-radius: 50%;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 1.5rem;
  font-weight: bold;
  color: white;
  text-shadow: 1px 1px 2px rgba(0,0,0,0.2);
  transition: transform 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.ball.placeholder {
  background-color: #e0e0e0;
  color: #aaa;
  text-shadow: none;
}

.ball.color-1 { background-color: #fbc400; } /* 1-10 */
.ball.color-2 { background-color: #69c8f2; } /* 11-20 */
.ball.color-3 { background-color: #ff7272; } /* 21-30 */
.ball.color-4 { background-color: #aaa; }    /* 31-40 */
.ball.color-5 { background-color: #b0d840; } /* 41-45 */

button#generate-btn {
  padding: 1rem 2rem;
  font-size: 1.2rem;
  font-weight: bold;
  background-color: #4a90e2;
  color: white;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  transition: background-color 0.2s, transform 0.1s;
}

button#generate-btn:hover {
  background-color: #357abd;
}

button#generate-btn:active {
  transform: scale(0.98);
}