:root {
  --gradient: linear-gradient(hsl(249, 99%, 64%), hsl(278, 94%, 30%));
  --red-error: hsl(0, 100%, 66%);
  --white: hsl(0, 100%, 100%);
  --light-grayish-violet: hsl(270, 3%, 87%);
  --dark-grayish-violet: hsl(279, 6%, 55%);
  --very-dark-violet: hsl(278, 68%, 11%);
  --font-family: 'Space Grotesk', sans-serif;
  --font-weight: 500;
  --font-size-body: 18px;
}

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

body {
  font-family: var(--font-family);
  font-size: var(--font-size-body);
  background-color: var(--white);
}

img {
  max-width: 100%;
  display: block;
}

input,
button {
  font-family: inherit;
  font-size: inherit;
  border: 1px solid var(--light-grayish-violet);
  border-radius: 8px;
}

input::placeholder {
  color: var(--dark-grayish-violet);
  opacity: 0.5;
}

.main-container {
  display: grid;
  min-height: 100vh;
}

.card-display {
  position: relative;
  color: var(--white);
  background-image: url('./images/bg-main-mobile.png');
  background-repeat: no-repeat;
  background-size: cover;
  height: 240px;
  padding: 20px;
}

.card {
  position: absolute;
  width: 286px;
  height: 157px;
  border-radius: 8px;
  box-shadow: 0 15px 30px rgba(0, 0, 0, 0.15);
  letter-spacing: 1.5px;
}

.card-back {
  background: url('./images/bg-card-back.png') no-repeat center/cover;
  top: 32px;
  right: 16px;
}

.card-back .card-cvc {
  position: absolute;
  top: 71px;
  right: 36px;
  font-size: 0.6em;
}

.card-front {
  background: url('./images/bg-card-front.png') no-repeat center/cover;
  top: 126px;
  left: 16px;
  padding: 18px;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  gap: 15px;
  z-index: 10;
}

.card-front .card-logo {
  position: absolute;
  top: 18px;
  left: 18px;
  width: 54px;
}

.card-front .card-number {
  font-size: 1.1em;
}

.card-front .card-details {
  display: flex;
  justify-content: space-between;
  text-transform: uppercase;
  font-size: 0.6em;
}

.form-container {
  padding: 24px;
  padding-top: 90px;
}

.card-form {
  display: grid;
  gap: 20px;
  max-width: 380px;
  margin: 0 auto;
}

.form-group {
  display: grid;
  gap: 8px;
}

.form-group label {
  text-transform: uppercase;
  font-size: 0.75em;
  letter-spacing: 2px;
  color: var(--very-dark-violet);
}

.form-group input {
  padding: 12px;
  width: 100%;
}

.form-group input:focus {
  outline: none;
  border-color: transparent;
  background-image: var(--gradient);
  background-origin: border-box;
  background-clip: content-box, border-box;
}

.expiry-cvc-group {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

#expiry-date-group {
  display: flex;
  gap: 10px;
}

.error-message {
  color: var(--red-error);
  font-size: 0.7em;
  margin-top: -12px;
  min-height: 1em;
}

.input-error {
  border-color: var(--red-error) !important;
}

.submit-btn {
  background-color: var(--very-dark-violet);
  color: var(--white);
  padding: 16px;
  cursor: pointer;
  width: 100%;
  margin-top: 8px;
  transition: background-color 0.3s ease;
}

.submit-btn:hover {
  background-color: hsl(278, 68%, 20%);
}

.completed-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: 20px;
}

.completed-state h2 {
  text-transform: uppercase;
  letter-spacing: 3px;
  color: var(--very-dark-violet);
  margin-top: 10px;
}

.completed-state p {
  color: var(--dark-grayish-violet);
}

.hidden {
  display: none !important;
}

/* --- DESKTOP LAYOUT  --- */
@media (min-width: 1000px) {
  .main-container {
    grid-template-columns: 1fr 2fr;
  }

  .card-display {
    background-image: url('./images/bg-main-desktop.png');
    height: 100%;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: flex-end;
    gap: 35px;
    overflow: visible;
  }

  .card {
    position: static;
    width: 447px;
    height: 245px;
    padding: 28px;
    letter-spacing: 2px;
  }

  .card-front {
    order: 1;
    transform: translateX(60px);
  }

  .card-back {
    order: 2;
    transform: translateX(140px);
  }

  .card-front .card-logo {
    width: 84px;
    top: 28px;
    left: 28px;
  }

  .card-front .card-number {
    font-size: 1.6em;
  }

  .card-front .card-details {
    font-size: 0.8em;
  }

  .card-back .card-cvc {
    top: 111px;
    right: 56px;
    font-size: 0.8em;
  }

  .form-container {
    display: grid;
    place-items: center;
    padding: 0;
  }
}