* {
  margin: 0;
  padding: 0;
}

body {
  background: linear-gradient(to top, #0d1b2a, #2274a599, #85aab644);
  min-height: 100vh;
}

main {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100vh;
}

#board {
  display: grid;
  grid-template-columns: repeat(9, 40px);
  grid-template-rows: repeat(9, 40px);
  gap: 2px;
  margin: 20px auto;
  width: fit-content;
  height: fit-content;
  outline: 2px solid #000;
  background-color: #f5f5f5;
}

.cell {
  width: 40px;
  height: 40px;
  text-align: center;
  font-size: 20px;
  border: 1px solid #ccc;
  line-height: 40px;
  cursor: pointer;
  font-size: 1.5em;
}

#controls {
  display: flex;
  justify-content: space-between;
  margin-top: 20px;
}

.number-button {
  width: 40px;
  height: 40px;
  font-size: 1.5em;
}

#mode {
  margin: 20px 0;
}

.mode-button {
  width: calc(100% / 3);
  height: 40px;
  font-size: 1.5em;
}

#reset-button {
  width: 100%;
  height: 40px;
  font-size: 1.5em;
}