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

body {
  margin: 0;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 10;
  background-color: rgba(0, 0, 0, 0.5);
  display: flex;
  justify-content: center;
  align-items: center;
  font-family: "Segoe UI", Arial, sans-serif;
  font-size: 1.1rem;
}

aside {
  background-color: white;
  width: 30rem;
  margin: 1.5rem;
  padding: 1.6rem;
  box-shadow: 0 5px 15px #333333;
  border-radius: 10px;
}

h1 {
  margin: 0 0 1.5rem 0;
  text-align: center;
}

#historical-event-name {
  font-weight: bold;
}

#days-input {
  display: block;
  width: 100%;
  font-size: 1.2rem;
  padding: 0.3rem 0.5rem;
  border: 2px solid #a6a6a6;
  border-radius: 5px;
  outline: none;
}

#days-input:focus {
  border-color: #595959;
}

#output-area p {
  text-align: center;
}

#output-date {
  font-size: 1.25rem;
  white-space: nowrap;
}

#confirm-btn, #retry-btn {
  display: block;
  color: white;
  margin: 2rem auto 0 auto;
  padding: 0.5rem 0.8rem;
  border: none;
  border-radius: 5px;
  font-size: 1rem;
  font-weight: bold;
}

#confirm-btn {
  background-color: #009900;
}

#confirm-btn:hover {
  background-color: #007000;
}

#confirm-btn:active {
  background-color: #005200;
}

#retry-btn {
  background-color: #f57a00;
}

#retry-btn:hover {
  background-color: #c76300;
}

#retry-btn:active {
  background-color: #a35200;
}

#confirm-btn:disabled, #retry-btn:disabled {
  background-color: gray;
}