body {
  text-align: center;
  margin: 0;
  padding: 0;
  font-family: Arial, sans-serif;
}

/* Headings responsive */
h1 {
  
  margin-top: 20px;
}
h2 {
  
  margin-top: 10px;
}

/* Button container */
.btn-container {
  display: flex;
  flex-direction: column; /* stack lines */
  align-items: center;
  margin-top: 30px;
}

.line-1,
.line-2 {
  display: flex;
  flex-wrap: wrap; /* allow wrapping on small screens */
  justify-content: center;
}

/* Buttons */
.btn {
  width: 20vw;
  height: 20vw;
  max-width: 200px;
  max-height: 200px;
  min-width: 100px;
  min-height: 100px;

  border-radius: 20%;
  border: 8px solid black;
  margin: 1rem;

  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 2rem;
  cursor: pointer;
}

/* Colors */
.yellow {
  background-color: #f99b45;
}
.red {
  background-color: #d95980;
}
.blue {
  background-color: rgb(194, 222, 138);
}
.purple {
  background-color: #819ff9;
}

/* Flash effects */
.flash {
  background-color: white !important;
  box-shadow: 0 0 20px #fff;
  transition: background-color 0.2s;
}
.userFlash {
  background-color: green !important;
  transition: background-color 0.2s;
}

/* 📱 Mobile optimization */
@media (max-width: 600px) {
  h1 {
    font-size: 6vw;
  }
  h2 {
    font-size: 4vw;
  }
  .btn {
    width: 35vw;
    height: 35vw;
    margin: 0.5rem;
  }
}

/* 💻 Tablets */
@media (max-width: 900px) {
  .btn {
    width: 25vw;
    height: 25vw;
  }
}