:root {
  --clr-cyan-300: #8fe3f9;
  --clr-cyan-400: #71c0d4;
  --clr-cyan-500: #4d97a9cc;
  --clr-cyan-600: #4d97a9f5;

  --clr-purple-300: #d9b8ff;
  --clr-purple-400: #b18bdd;
  --clr-purple-600: #855fb1;

  --clr-slate-300: #d1d1df;
  --clr-slate-600: #87879d;
  --clr-slate-900: #28283d;

  --clr-white: #fafafa;
}

html {
  box-sizing: border-box;
  font-size: 100%;
  overflow-x: hidden;
}

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

body {
  margin: 0;
  color: var(--clr-slate-900);
  background-color: var(--clr-white);
  font-family: 'Red Hat Display', sans-serif;
}

a {
  text-decoration: none;
}

p,
h1, h2, h3, h4, h5, h6 {
  margin: 0;
  font-size: inherit;
}

img {
  max-inline-size: 100%;
  block-size: auto;
  vertical-align: middle; /* remove extra whitespace */
  font-style: italic; /* alt text will be... italic! */
  background-repeat: no-repeat; /* slow connexion */
  background-size: cover; /* slow connexion */
  shape-margin: 0.75rem; /* for floating images */
}

ul {
  list-style-type: none;
}

.overlay {
  position: absolute;
  z-index: 999;
  background: var(--clr-white);
  width: 100%;
  height: 100%;
  animation: reveal 1s ease-in forwards;
  transform-origin: bottom;
}

.container {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.container-sm {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
}

main {
  animation: growIn 2s cubic-bezier(0.075, 0.82, 0.165, 1) forwards;
  transform: scale(.4);
}

/* HEADER */
header {
  padding: 3em 2em 2em;
  text-align: center;
}

.header__logo a {
  display: inline-block;
}

/* HERO */
.hero {
  padding: 2em;
}

.hero__container {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
}
 
.hero__img {
  position: relative;
  margin-bottom: 3rem;
}

.hero__img > img {
  max-inline-size: unset;
  inline-size: 105vw;
}

.hero__img-left,
.hero__img-right {
  display: none;
}

.hero__description {
  margin-block: 1.5rem;
}

.hero__btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 1rem;
}

.btn {
  display: inline-block;
  padding: 1.0625em 2.5em 0.9375em;
  background-color: var(--clr-cyan-600);
  color: var(--clr-white);
  text-align: center;
  font-size: 1rem;
  font-weight: 900;
  line-height: 150%;
  border-radius: 100px;
  transition: background-color 0.3s ease-in-out;
}

.btn span {
  color: var(--clr-cyan-300);
}

.btn-sm {
  background-color: var(--clr-purple-600);
}

.btn-ftr {
  background-color: var(--clr-purple-600);
}

.btn-ftr span {
  color: var(--clr-purple-300);
}

.btn:hover, 
.btn:active, 
.btn:focus {
  background-color: var(--clr-cyan-400);
}

.btn-sm:hover,
.btn-sm:active,
.btn-sm:focus,
.btn-ftr:hover,
.btn-ftr:active,
.btn-ftr:focus {
  background-color: var(--clr-purple-400);
}

/* INTRODUCTION */
.introduction {
  padding: 2em 2em 4em;
  text-align: center;
} 
  
.introduction__section-indicator {
  position: relative;
  margin-block-start: 5rem;
  margin-block-end: 3.875rem;
}

.introduction__section-indicator > div,
.download-app__section-indicator > div {
  width: 3.5rem;
  height: 3.5rem;
  background-color: var(--clr-white);
  border: 1px solid var(--clr-slate-300);
  border-radius: 50%;
}

.introduction__section-indicator > div::after,
.download-app__section-indicator > div::after {
  position: absolute;
  top: -5rem;
  content: '';
  background-color: var(--clr-slate-300);
  width: 1px;
  height: 5rem;
}

.introduction__section-indicator > div > span,
.download-app__section-indicator > div > span {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-weight: 900;
  color: var(--clr-slate-600);
  font-size: 1rem;
}

.introduction__cards {
  display: grid;
  grid-template-columns: repeat(2, auto);
  gap: 1rem;
  margin-block-end: 4rem;
}

.card {
  border-radius: 10px;
  background-repeat: no-repeat;
  background-size: 106%;
  transition: background-size 800ms;
  inline-size: 9.25rem;
  block-size: 9.25rem;
}

.card:hover {
  background-size: 120%;
}

.card1 {
  background-image: url('./assets/desktop/image-woman-in-videocall.jpg');
}

.card2 {
  background-image: url('./assets/desktop/image-women-videochatting.jpg');
}
  
.card3 {
  background-image: url('./assets/desktop/image-men-in-meeting.jpg');
}

.card4 {
  background-image: url('./assets/desktop/image-man-texting.jpg');
}

.introduction__title {
  margin: 1rem 0 2rem;
}

/* DOWNLOAD-APP */
.download-app {
  padding: 0 2em 4em;
  margin-block-start: 6.75rem;
  background-repeat: no-repeat;
  background-image: linear-gradient(90deg, rgba(77, 151, 169, 0.9) 0%, rgba(77, 151, 169, 0.9) 100%), url('./assets/mobile/image-footer.jpg');
  background-size: cover;
  background-position: center top;
}

.download-app__description {
  margin-block: 1.5rem;
}

.download-app__section-indicator {
  position: relative;
  margin-block-start: -1.75rem;
  margin-block-end: 2.5rem;
}

/* Utilities */
.visually-hidden {
  position: absolute;
  inline-size: 1px;
  block-size: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

.txt-1 {
  font-size: 2.5rem;
  font-weight: 900;
  line-height: 110%;
}

.txt-2 {
  color: var(--clr-slate-600);
  font-size: 1rem;
  font-weight: 500;
  line-height: 150%;
}

.txt-3 {
  color: var(--clr-cyan-600);
  font-size: 0.75rem;
  font-weight: 900;
  line-height: 110%;
  letter-spacing: 4px;
  text-transform: uppercase;
}

.txt-4 {
  font-size: 2rem;
  font-weight: 900;
  line-height: 110%;
}

.txt-5 {
  color: var(--clr-white);
  font-size: 2rem;
  font-weight: 900;
  line-height: 110%;
}

.txt-6 {
  color: var(--clr-white);
  font-size: 1rem;
  font-weight: 500;
  line-height: 150%;
}

.ws-1 {
  word-spacing: 1px;
}

.gr-txt {
  background: linear-gradient(92.19deg, #855FB1 -15.84%, #4D96A9 114.64%);
  background-clip: text;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

/* MEDIA QUERIES */
@media screen and (width >= 31.25em) {
  .hero__description,
  .introduction__description,
  .download-app__description {
    padding-inline: 3.125em;
  }
}

@media screen and (width >= 48em) {
  .hero {
    padding: 2em 2em 4em;
  }

  .hero__img {
    margin-block-end: 4.5rem;
  }

  .hero__title {
    font-size: 3rem;
  }

  .hero__btn {
    flex-direction: row;
  }

  .introduction {
    padding: 3.5em 2em 4em;
  }

  .introduction__cards {
    grid-template-columns: repeat(4, auto);
  }

  .introduction__cards .card {
    inline-size: 10rem;
    block-size: 10rem;
  }

  .introduction__subtitle {
    font-size: 0.875rem;
  }

  .introduction__title {
    font-size: 2.25rem;
  }

  .download-app__title {
    font-size: 2.25rem;
  }

  .download-app {
    background-image: linear-gradient(90deg, rgba(77, 151, 169, 0.9) 0%, rgba(77, 151, 169, 0.9) 100%), url(./assets/tablet/image-footer.jpg);
  }

  .hero__description,
  .introduction__description,
  .download-app__description {
    padding-inline: 11.875em;
  }
}


@media screen and (width >= 71.875em) {
  header {
    padding: 5em 0 0;
  }

  .hero {
    padding: 4em 2em 4em;
  }

  .hero__container {
    flex-direction: row;
    gap: 2rem;
  }

  .hero__container > * {
    flex-basis: 100%;
  }

  .hero__img {
    display: none;
  }

  .hero__img-left {
    justify-content: left;
    margin-block-start: -3.75rem;
    margin-inline-start: -4.3%;
    animation: slideInFromLeft 1s ease-in-out;
  }

  .hero__img-right {
    justify-content: right;
    margin-block-end: -3.125rem;
    margin-inline-end: -4.3%;
    animation: slideInFromRight 1s ease-in-out;
  }

  .hero__img-left,
  .hero__img-right {
    display: flex;
    flex-basis: 100%;
  }

  .hero__text {
    padding-block: 2.25em;
    animation: slideInFromBottom 1s ease-in-out;
  }

  .hero__title {
    font-size: 4em;
  }

  .hero__description {
    font-size: 1.125rem;
    margin-block: 1.875rem;
  }

  .introduction {
    padding: 1.25em 10em 4.5em;
  }

  .introduction__cards {
    margin-block-end: 5rem;
    gap: 2rem;
  }

  .introduction__cards .card {
    inline-size: 16rem;
    block-size: 15.5rem;
  }

  .introduction__subtitle {
    font-size: 1rem;
  }

  .introduction__title {
    font-size: 2.5rem;
    margin-block-end: 2.25rem;
  }

  .introduction__description {
    font-size: 1.125rem;
  }

  .download-app {
    background-image: linear-gradient(90deg, rgba(77, 151, 169, 0.9) 0%, rgba(77, 151, 169, 0.9) 100%), url(./assets/desktop/image-footer.jpg);
    background-size: cover;
    padding: 0 10em 7em;
  }

  .download-app__section-indicator {
    margin-block-end: 5.25rem;
  }

  .download-app__text {
    display: grid;
    grid-template-columns: 2fr 2fr 1fr;
    align-items: start;
    text-align: left;
    gap: 3.75em;
  }

  .download-app__title {
    font-size: 2.5rem;
    max-inline-size: 16ch;
  }

  .download-app__description {
    margin-block: 0;
    font-size: 1.125rem;
    max-inline-size: 30ch;
  }

  .hero__description,
  .download-app__description {
    padding-inline: 0;
  }
}


@media screen and (width >= 112.5em) {
  .header__logo img {
    inline-size: 8.375rem;
  }

  .hero__img-left {
    margin-inline-start: -3.3%;
  }

  .hero__img-right {
    margin-inline-end: -3.3%;
  }

  .hero__img-left img,
  .hero__img-right img {
    inline-size: 30.125rem;
  }

  .hero__title {
    font-size: 4.5rem;
  }

  .hero__description {
    font-size: 1.25rem;
  }

  .introduction__section-indicator > div,
  .download-app__section-indicator > div {
    inline-size: 4.25rem;
    block-size: 4.25rem;
  }

  .introduction__section-indicator > div::after, 
  .download-app__section-indicator > div::after {
    block-size: 6.25rem;
    top: -6.25rem;
  }

  .introduction__section-indicator {
    margin-block-start: 6.25rem;
    margin-block-end: 5rem;
  }

  .introduction__cards .card {
    inline-size: 17rem;
  }

  .introduction__cards {
    gap: 2.375rem;
  }

  .introduction__cards {
    margin-block-end: 5rem;
  }

  .introduction__subtitle {
    font-size: 1.125rem;
  }

  .introduction__title {
    font-size: 3rem;
  }

  .introduction__description {
    padding-block-end: 5em;
    font-size: 1.125rem;
  }

  .download-app__title {
    font-size: 2.625rem;
  }

  .download-app__description {
    font-size: 1.25rem;
  }

  .introduction__description {
    padding-inline: 24.375em;
  }

  .download-app__section-indicator {
    margin-block-start: -2.125rem;
  }
}


/* ANIMATIONS */
@keyframes reveal {
  0% {
    transform: scaleY(1);
  }

  100% {
    transform: scaleY(0);
  }
}

@keyframes growIn {
  100% {
    transform: scale(1);
  }
}

@keyframes slideInFromLeft {
  0% {
    transform: translateX(-100%);
  }

100% {
    transform: translateX(0);
  }
}

@keyframes slideInFromRight {
  0% {
    transform: translateX(100%);
  }

100% {
    transform: translateX(0);
  }
}

@keyframes slideInFromBottom {
  0% {
    transform: translateY(100%);
  }

100% {
    transform: translateX(0);
  }
}