:root {
  --text-color: white;

  --accent-green: #c1f2c5 !important;
  --accent-yellow: #f5efa1 !important;
  --accent-pink: #fab2ff !important;
  --accent-blue: #3b99c9 !important;
  --accent-purple: #9961d1 !important;

  --background-color-blue: hsl(200, 100%, 45%);
  --background-color-dark-blue: hsl(220, 100%, 45%);

  --background-color-red: hsl(360, 100%, 65%);
  --background-color-dark-red: hsl(255, 45%, 35%);
  --background-color-green: hsl(140, 65%, 35%);
  --background-color-dark-green: hsl(160, 95%, 24%);
  --background-color-purple: hsl(270, 55%, 60%);
  --background-color-dark-purple: hsl(240, 40%, 60%);
  --background-color-blue: hsl(200, 100%, 45%);
  --background-color-dark-blue: hsl(220, 100%, 45%);

  --font-size-s: 1.2rem;
  --font-size-normal: 1.5rem;
  --line-height-normal: 1.5;

  --width-limit: 600px;
  --width-limit-l: 800px;
  --max-width-limit: 1440px;

  --spacing-xxxs: 0.25rem;
  --spacing-xxs: 0.5rem;
  --spacing-xs: 1rem;
  --spacing-s: 2rem;
  --spacing-m: 3rem;
  --spacing-l: 4rem;
  --spacing-xl: 6rem;
}

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

body {
  max-width: 100%;
  margin: 0;
  padding: 0;
  color: var(--text-color);
  font-size: 16px;
  font-family: Inter, system-ui, sans-serif;
  font-weight: 300;
  line-height: var(--line-height-normal);
  background: linear-gradient(135deg, var(--background-color), var(--background-color-dark));
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body.green {
  background: linear-gradient(
    135deg,
    var(--background-color-green),
    var(--background-color-dark-green)
  );
}

body.red {
  background: linear-gradient(
    135deg,
    var(--background-color-red),
    var(--background-color-dark-red)
  );
}

body.purple {
  background: linear-gradient(
    135deg,
    var(--background-color-purple),
    var(--background-color-dark-purple)
  );
}

nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-weight: 400;
  padding: var(--spacing-xs) var(--spacing-s);
  z-index: 10;
}

nav ul li:before {
  content: '';
}

button {
  background-color: #f5ee9e;
  color: black;
  padding: var(--spacing-xxxs) var(--spacing-m);
  border: none;
  border-radius: var(--spacing-xxs);
  font-size: var(--font-size-normal);
  cursor: pointer;
  height: auto;
  min-height: var(--spacing-m);
  box-shadow: 0 var(--spacing-xxxs) var(--spacing-s) rgba(0, 0, 0, 0.2);
  transition: 0.2s;
}

button:hover {
  box-shadow: 0 var(--spacing-xxxs) var(--spacing-s) rgba(0, 0, 0, 0.6);
  transition: 0.2s;
}

h1,
h2,
h3,
h4,
h5,
h6,
button {
  font-weight: 500;
}

p {
  margin-bottom: var(--spacing-m);
}

a {
  color: white;
}

strong {
  font-weight: 600;
}

ol li {
  margin-left: var(--spacing-s);
  margin-bottom: var(--spacing-xs);
}

ul li {
  list-style: none;
  position: relative;
  padding-left: var(--spacing-s);
  margin-bottom: var(--spacing-s);
}

ul li:before {
  content: '> ';
  position: absolute;
  left: 0;
  top: 0;
}

hr {
  color: white;
  width: 80%;
  max-width: var(--width-limit-l);
  margin: 0 var(--spacing-s);
  margin: 0 auto;
}

section {
  font-size: var(--font-size-normal);
}

footer {
  text-align: center;
  padding: var(--spacing-s);
  font-size: 1rem;
}

footer p {
  font-size: 1rem;
}

nav .logo {
  font-size: var(--font-size-s);
  position: fixed;
  top: var(--spacing-xs);
  left: var(--spacing-m);
  pointer-events: none;
}

nav .nav-links {
  position: fixed;
  top: var(--spacing-xs);
  right: var(--spacing-m);
  display: flex;
  gap: var(--spacing-s);
}

nav .nav-links a {
  font-size: var(--font-size-s);
  text-decoration: none;
  color: var(--text-color);
}

.hero {
  max-width: var(--max-width-limit);
  padding: 6rem var(--spacing-s) 10rem var(--spacing-s);
  margin: 0 auto;
}

.hero h1 {
  font-size: 5rem;
  margin-bottom: var(--spacing-s);
  line-height: 1.2;
  font-weight: 300;
}

.hero p {
  font-size: var(--font-size-normal);
  margin-bottom: var(--spacing-s);
}

.book-container {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  margin-top: 10rem;
}

.book-container .book:hover {
  transform: rotate(4deg);
  transition: 0.6s;
}

.book-container .book {
  width: 30rem;
  height: 45rem;
  display: inline-block;
  position: relative;
  vertical-align: top;
  border-radius: 0 var(--spacing-xxs) var(--spacing-xxs) 0;
  box-shadow: 0 var(--spacing-xxxs) var(--spacing-s) rgba(0, 0, 0, 0.35);
  transition: 0.4s;
}

.book-container .book .link {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(
    to right,
    rgba(0, 0, 0, 0.02) 0%,
    rgba(0, 0, 0, 0.05) 0.75%,
    rgba(255, 255, 255, 0.5) 1%,
    rgba(255, 255, 255, 0.6) 1.3%,
    rgba(255, 255, 255, 0.5) 1.4%,
    rgba(255, 255, 255, 0.3) 1.5%,
    rgba(255, 255, 255, 0.3) 2.4%,
    rgba(0, 0, 0, 0.05) 2.7%,
    rgba(0, 0, 0, 0.05) 3.5%,
    rgba(255, 255, 255, 0.3) 4%,
    rgba(255, 255, 255, 0.3) 4.5%,
    rgba(244, 244, 244, 0.1) 5.4%,
    rgba(244, 244, 244, 0.1) 99%,
    rgba(144, 144, 144, 0.2) 100%
  );
  box-shadow: inset 0 -1px var(--spacing-xxxs) rgba(0, 0, 0, 0.15);
}

.book-container .book .cover {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100%;
  border-radius: 0 var(--spacing-xxs) var(--spacing-xxs) 0;
  overflow: hidden;
}

.book-container .book .cover img {
  min-width: 100%;
  min-height: 100%;
}

.intro-text {
  max-width: var(--width-limit);
  margin: var(--spacing-xl) auto;
  padding: 0 var(--spacing-s);
  font-size: var(--font-size-normal);
  line-height: 1.5;
}

.features {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-s);
  padding: var(--spacing-l) var(--spacing-s);
  max-width: var(--width-limit);
  margin: 0 auto;
  font-size: var(--font-size-normal);
  line-height: var(--line-height-normal);
}

.features div:last-child {
  margin-bottom: 0;
}

.features .feature {
  max-width: 40rem;
  margin: 0 auto;
  margin-bottom: 6rem;
}

.features .feature svg {
  color: white !important;
  display: block;
  width: 25%;
  height: auto;
  margin: 0 auto;
  margin-bottom: var(--spacing-m);
}

.features .feature h2 {
  font-size: 2.25rem;
  margin-bottom: var(--spacing-xs);
}

.book-structure {
  max-width: var(--width-limit);
  margin: 0 auto;
  margin-top: var(--spacing-xl);
  margin-bottom: var(--spacing-xl);
  padding: 0 var(--spacing-s);
  display: block;
}

.book-structure h2 {
  margin-bottom: var(--spacing-xs);
}

.book-structure ol {
  font-size: var(--font-size-s);
}

.sales {
  margin: 0 auto;
  width: 100%;
  max-width: var(--width-limit-l);
  position: relative;
  text-align: center;
  margin-top: var(--spacing-l);
  font-size: var(--font-size-normal);
}

.pricing {
  text-align: center;
  margin-bottom: 8rem;
}

.pricing svg {
  display: block;
  width: 100%;
  margin-bottom: 2rem;
}

.pricing .sales-price {
  text-align: center;
  font-size: 10rem;
  font-weight: 800;
  margin: var(--spacing-l) 0;
}

.pricing .sales-vendor {
  margin: 4rem 0;
}

.pricing .sales-vendor button {
  margin-bottom: var(--spacing-s);
}

.pricing .sales-vendor p {
  margin: 1rem 0;
  font-size: 0.8rem;
  font-style: italic;
}

.pricing .sales-box {
  color: black;
  background-color: white;
  text-align: left;
  border-radius: var(--spacing-xs);
  padding: var(--spacing-m);
  max-width: 30rem;
  margin: 0 auto;
  margin-top: var(--spacing-s);
  margin-bottom: var(--spacing-xl);
  box-shadow: 0 var(--spacing-xxxs) var(--spacing-s) rgba(0, 0, 0, 0.2);
}

.pricing h3 {
  font-size: 2rem;
  margin-bottom: 1.5rem;
}

.pricing ul li {
  font-size: var(--font-size-s);
  margin-bottom: 0.75rem;
}

.pricing .sales-box ul li:last-child {
  margin-bottom: 0;
}

.accent-green {
  background-color: var(--accent-green);
}

.accent-yellow {
  background-color: var(--accent-yellow);
}

.accent-pink {
  background-color: var(--accent-pink);
}

.accent-blue {
  color: white;
  background-color: var(--accent-blue);
}

.accent-purple {
  color: white;
  background-color: var(--accent-purple);
}

@media screen and (max-width: 900px) {
  :root {
    --font-size-normal: 1.3rem;
    --spacing-xs: 0.5rem;
    --spacing-xl: 3rem;
  }

  hr {
    width: 100%;
  }

  nav {
    align-items: baseline;
  }

  nav .logo {
    position: relative;
    top: 0;
    left: 0;
    font-size: 1rem;
  }

  nav .nav-links {
    position: relative;
    top: 0;
    right: 0;
  }

  nav .nav-links a {
    font-size: 1rem;
  }

  .book-container .book {
    width: 16rem;
    height: 24rem;
  }

  ul li {
    margin-bottom: 1rem;
  }

  .hero h1 {
    font-size: 3rem;
    margin-bottom: var(--spacing-s);
  }

  .pricing {
    padding: var(--spacing-s);
    margin-bottom: 0;
  }

  .pricing .sales-box {
    padding: var(--spacing-s);
  }

  .pricing .sales-price {
    font-size: 8rem;
  }
}