*,
*::before,
*::after {
  box-sizing: border-box;
}

* {
  margin: 0;
  padding: 0;
  line-height: 1.5;
}

body {
  font-family: "Open Sans", sans-serif;
  background-color: #1a1a2e;
  overflow: hidden;
  color: #fff;
}

/* header section */
.header__title {
  color: #fff;
  letter-spacing: -0.05rem;
  text-align: center;
  margin-top: 2rem;
}

/* main section */
.main {
  margin: 3rem auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
  width: 50%;
}

.container {
  display: flex;
  flex-wrap: wrap;
  width: 500px;
  height: 500px;
  box-shadow:
    rgba(0, 0, 0, 0.25) 0px 54px 55px,
    rgba(0, 0, 0, 0.12) 0px -12px 30px,
    rgba(0, 0, 0, 0.12) 0px 4px 6px,
    rgba(0, 0, 0, 0.17) 0px 12px 13px,
    rgba(0, 0, 0, 0.09) 0px -3px 5px;
  overflow: hidden;
}

.cell {
  /* border: 1px solid #ccc; */
  /* background-color: white; */
  background-color: #16213e;
  border: 1px solid #0f3460;
  transition: background-color 0.1s;
}

.button__container {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-top: 1rem;
}

.btn {
  border: none;
  padding: 0.5rem 1.4rem;
  border-radius: 1000000px;
  background-color: #6d28d9;
  transition: opacity 0.2s;
  color: #fff;
  font-family: inherit;
  font-size: 1rem;
  cursor: pointer;
}

.btn:hover {
  opacity: 0.8;
}

input[type="number"] {
  background-color: #16213e;
  border: 2px solid #6d28d9;
  color: #fff;
  border-radius: 1000000px;
  padding: 0.5rem 1rem;
}

@media (max-width: 700px) {
  body {
    overflow: auto;
  }
  .button__container {
    flex-wrap: wrap;
    justify-content: center;
  }
  .container {
    width: 90vw;
    height: 90vw;
  }
  main {
    width: 90%;
  }
}