*,
::before,
::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  background: #2a2a2a;
  padding: 36px 20px 160px;
  font-family: Lato, sans-serif;
  color: #f1f1f1;
}
.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 24px;
}
h1 {
  margin-bottom: 24px;
}
ol {
  font-size: 22px;
}
ol li {
  margin: 8px 0;
}
section {
  margin-bottom: 75px;
}
h2 {
  margin-bottom: 8px;
}
.subtitle {
  font-size: 18px;
  margin-bottom: 20px;
}
/* 1. */
.gradient-transition {
  width: 450px;
  height: 150px;
  background-image: linear-gradient(45deg, pink, orange);
  position: relative;
  z-index: 1;
  display: flex;
  justify-content: center;
  align-items: center;
}
.gradient-transition p {
  font-size: 36px;
  font-weight: 700;
  margin-bottom: 24px;
  color: #e6e6e6;
  text-shadow: 1px 1px 0px #111;
}
.gradient-transition::after {
  content: "";
  display: block;
  position: absolute;
  z-index: -1;
  width: 100%;
  height: 100%;
  background-image: linear-gradient(135deg, lightblue, purple);
  opacity: 0;
  transition: opacity 0.4s ease-out;
}
.gradient-transition:hover::after {
  opacity: 1;
}

/* 2. */
.block {
  width: 125px;
  height: 125px;
}

.b-1 {
  background-color: lightgreen;
}
.b-2 {
  background-color: lightskyblue;
  margin-top: -80px;
  margin-left: 40px;
}
.b-3 {
  background-color: violet;
  margin-top: -80px;
  margin-left: 80px;
}

/*3. */

.card-container {
  max-width: 600px;
  background: #f1f1f1;
  color: #111;
  padding: 30px;
  border-radius: 10px;
  box-shadow: 5px 5px 15px rgba(0, 0, 0, 0.3);
}

.card-container::after {
  content: "";
  display: block;
  clear: both;
}
.card-container h2 {
  margin-bottom: 10px;
}
.card-container p {
  line-height: 1.4;
}
img {
  width: 200px;
  height: 200px;
  object-fit: cover;
  border-radius: 50%;
  float: left;
  shape-outside: margin-box;
  /* Une marge négative montre que le texte est au-dessus */
  margin: 0 20px 5px 0;
}

/* 4. */
.inline-block {
    display: inline-block;
    width: 50px;
    height: 50px;
    background-color: red;
}
.ex-4 {
    margin-top: -35px;
}

/* 5. */
.ex-5-card {
    width: 300px;
    background-color: lightblue;
    color: #111;
    font-size: 18px;
    padding: 12px;
    border-radius: 5px;
    position: relative;
}
.absolute-item {
    width: 75px;
    height: 25px;
    background-color: red;
    /* Passe au-dessus des autres éléments block-static */
    position: absolute;
    top: 20px;
    /* transform / opacity / etc... peuvent créer des contextes d'empilement */
    /* transform: rotate(45deg) */
}


/* 6. */
.parent-context {
    position: relative;
    z-index: 1;
}
.child-context {
    width: 75px;
    height: 75px;
    position: absolute;
}
.ce-1{
    z-index: 3;
    background-color: crimson;
}
.ce-2 {
    z-index: 2;
    background-color: limegreen;
    top: 20px;
    left: 20px;
}
.ce-3 {
    z-index: 1;
    background-color: lightblue;
    top: 40px;
    left: 40px;
}