body {
  background: #f0f8ff;
  font-family: 'Segoe UI', sans-serif;
  transition: background 0.3s, color 0.3s;
}

body.dark {
  background: #1c1c1c;
  color: white;
}

.form-container {
  max-width: 500px;
  margin: 20px auto;
  padding: 30px;
  background: white;
  border-radius: 15px;
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.1);
  transition: all 0.3s;
}

body.dark .form-container {
  background: #2b2b2b;
}

.error {
  color: red;
  font-size: 0.9rem;
  opacity: 0;
  transform: translateY(-5px);
  transition: opacity 0.3s ease, transform 0.3s ease;
}

.error.animate-error:empty {
  opacity: 0;
}

.error.animate-error:not(:empty) {
  opacity: 1;
  transform: translateY(0);
}

input:valid {
  border-color: green !important;
}

input:invalid {
  border-color: red !important;
}

.toggle-password {
  position: absolute;
  top: 50%;
  right: 15px;
  transform: translateY(-50%);
  cursor: pointer;
  color: #aaa;
}

.theme-toggle {
  text-align: right;
}

.progress-bar {
  transition: width 0.4s;
}

/* Strength Meter */
.strength-meter {
  height: 5px;
  margin-top: 5px;
  border-radius: 5px;
  background: #eee;
  overflow: hidden;
}

.strength-meter div {
  height: 100%;
  transition: width 0.3s;
}

.strength-meter .weak {
  width: 33%;
  background: red;
}

.strength-meter .medium {
  width: 66%;
  background: orange;
}

.strength-meter .strong {
  width: 100%;
  background: green;
}

/* Slide animation */
.animate-slide {
  animation: slideFadeIn 0.7s ease forwards;
}

@keyframes slideFadeIn {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}