* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
}

:root {
  --bgcol: #37474f;
  --mcol0: #29b6f6;
  --mcol1: #2196f3;
  --mcol2: #1976d2;
  --txtcol0: #90a4ae;
  --txtcol1: #607d8b;
  --whitecol: #eceff1;
  --darkcol: #263238;
}

img {
  width: 120px;
  height: 120px;
}

body {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding-top: 15vh;
  background-color: var(--bgcol);
}

#puzzle_container {
  position: relative;
  width: 50vh;
  height: 50vh;
  background-color: var(--darkcol);
  border-radius: 8px;
  border: 1px solid var(--mcol0);
  box-shadow: 0px 8px 0px var(--mcol0);
}

.puzzle_block {
  position: absolute;
  left: 0;
  top: 0;
  width: 33.4%;
  height: 33.4%;
  background-color: var(--txtcol1);
  color: var(--whitecol);
  font-size: 10vh;
  font-weight: bold;
  text-align: center;
  cursor: pointer;
  user-select: none;
  transition: left 0.3s, top 0.3s;
}

/*difficulty container*/
#difficulty_container {
  display: flex;
  flex-direction: row;
  width: 50vh;
  height: 10vh;
  background-color: var(--darkcol);
  border-radius: 8px;
  margin-top: 22px;
}
.difficulty_button {
  flex-grow: 1;
  background-color: inherit;
  color: var(--mcol2);
  text-align: center;
  font-size: 3vh;
  font-weight: bold;
  padding-top: 5%;
  margin: 4px;
  cursor: pointer;
  transition: font-size 0.3s;
}
.difficulty_button:hover {
  opacity: 0.8;
  font-size: 3.5vh;
}
.difficulty_button.active {
  background-color: inherit;
  color: var(--mcol0);
}
.mute-button {
  position: fixed;
  top: 20px;
  right: 20px;
  background: none;
  border: none;
  color: white;
  font-size: 30px;
  cursor: pointer;
  transition: transform 0.2s ease;
}

.mute-button:hover {
  transform: scale(1.1);
}

.exit-button {
  position: fixed;
  top: 20px;
  left: 20px;
  background: none;
  border: none;
  color: white;
  font-size: 30px;
  cursor: pointer;
  transition: transform 0.2s ease;
}

.exit-button:hover {
  transform: scale(1.1);
}