:root {
  --bg-color: #f0f4f8;
  --text-color: #2d3748;
  --card-bg: #ffffff;
  --btn-bg: #4299e1;
  --btn-text: #ffffff;
  --progress-bg: #e2e8f0;
  --progress-fill: #48bb78;
  --cell-bg: #edf2f7;
  --cell-hover: #e2e8f0;
  --correct-bg: #f56565;
}

.dark-mode {
  --bg-color: #1a202c;
  --text-color: #e2e8f0;
  --card-bg: #2d3748;
  --btn-bg: #4299e1;
  --btn-text: #ffffff;
  --progress-bg: #4a5568;
  --progress-fill: #48bb78;
  --cell-bg: #4a5568;
  --cell-hover: #718096;
  --correct-bg: #f56565;
}

body {
  font-family: "Noto Sans KR", sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
  transition: background-color 0.3s ease;
}

#app {
  width: 90%;
  max-width: 500px;
}

.card {
  background-color: var(--card-bg);
  border-radius: 15px;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  padding: 2rem;
  margin-bottom: 1rem;
  transition: all 0.3s ease;
}

#theme-toggle {
  position: absolute;
  top: 1rem;
  right: 1rem;
  font-size: 1.5rem;
  cursor: pointer;
}

h1 {
  font-size: 2rem;
  margin-bottom: 1rem;
  text-align: center;
}

.btn {
  display: block;
  width: 100%;
  padding: 0.75rem;
  margin-top: 1rem;
  background-color: var(--btn-bg);
  color: var(--btn-text);
  border: none;
  border-radius: 5px;
  font-size: 1rem;
  cursor: pointer;
  transition: background-color 0.3s ease;
}

.btn:hover {
  opacity: 0.9;
}

#header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
}

#progress {
  flex-grow: 1;
  margin-left: 1rem;
}

#progressBar {
  height: 8px;
  background-color: var(--progress-bg);
  border-radius: 4px;
  overflow: hidden;
}

#progressBarFill {
  height: 100%;
  background-color: var(--progress-fill);
  width: 100%;
  transition: width 0.1s linear;
}

#grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.5rem;
}

.cell {
  aspect-ratio: 1;
  background-color: var(--cell-bg);
  border-radius: 5px;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 1.5rem;
  cursor: pointer;
  user-select: none;
  transition: background-color 0.3s ease;
}

.cell:hover {
  background-color: var(--cell-hover);
}

.correct {
  background-color: var(--correct-bg);
  color: white;
}

.correct:hover {
  background-color: var(--correct-bg);
  color: white;
}

.cell {
  /* border: 1px solid black; */
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 24px;
  cursor: pointer;
}

.correct {
  background-color: red;
}

.titleHighestLevel {
  text-align: center;
}

#inGameHighestLevel {
  display: flex;
  justify-content: center;
  background-color: var(--btn-bg);
  padding: 5px 10px;
  border-radius: 15px;
  font-size: 0.9em;
  color: #ffffff;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
  transition: all 0.3s ease;
}

.dark-mode #inGameHighestLevel {
  background-color: var(--cell-bg);
  color: var(--text-color);
}

#logo {
  width: 100px;
  height: 100px;
  border-radius: 20%;
  justify-content: center;
  display: block;
  margin: 0 auto;
}

#version {
  font-size: 0.9rem;
  color: #888;
  text-align: center;
  margin-top: -10px;
  font-weight: normal;
  font-style: italic;
}

#copyright {
  font-size: 0.7rem;
  color: #888;
  text-align: center;
  margin-top: 10px;
  font-weight: normal;
}

#copyright {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 5px;
}

#copyright a {
  color: inherit;
  text-decoration: none;
}

#copyright i {
  font-size: 1.2em;
}

@media (max-width: 480px) {
  #app {
    width: 95%;
  }

  .card {
    padding: 1rem;
  }

  .cell {
    font-size: 1.2rem;
  }
}