:root {
  --primary-dark:rgb(9, 13, 90);
  --primary:rgb(43, 48, 150);

  --s1: 0.6rem;
  --s2: 1rem;
  --s3: 1.5rem;
  --s4: 3.5rem;
}

html, body, h1, h2, h3 {
  margin: 0;
  padding: 0;
}

body {
  font-family: Arial, Helvetica, sans-serif;
  background-color: lightgray;
}

header {
  background-color: var(--primary-dark);
  color: white;
  padding: 0.8rem;
}

.astronomy-picture {
  background-color: white;
  margin: var(--s4) var(--s2);
  padding: var(--s1) var(--s2);
  border-radius: var(--s1);
}

.astronomy-picture img {
  max-height: 400px;
  max-width: 50%;
  object-fit: cover;
}

article {
  display: flex;
}

.text-container {
  padding: var(--s2);
}

.pictures-container {
  display: flex;
  flex-wrap: wrap;
}

.picture-container {
  flex: 0 0 25%;
}

.picture-container img {
  object-fit: cover;
  width: 100%;
  height: 100%;
}

/* Stile un po' bruttino, ma è giusto per mostrare un esempio di modal window! */
#picture-details-container {
  display: none;
  /* In JavaScript cambio proprietà display */
  /* display: flex; */
  height: 100vh;
  width: 100%;
  z-index: 9;
  position: fixed;
  top: 0;
  background-color: rgba(0,0,0,0.8);
  justify-content: center;
  align-items: center;
}

.picture-details {
  background-color: white;
  width: 90%;
  height: 90vh;
  overflow: hidden;
}