/* GLOBAL STYLES */
html, body {
  font-family: 'Inter', "Helvetica", Arial, sans-serif;
  text-align: center;
  margin: 0;
  padding: 0; /* no padding */
  letter-spacing: 0.2px;
  height: 100%;
}

/* LAYOUT STRUCTURE (for sticky footer) */
body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

/* GLOBAL LINK STYLE */
a {
  color: #00B0FF;
  text-decoration: none;
  transition: opacity 0.3s, text-decoration 0.3s;
}

a:hover {
  text-decoration: underline;
  opacity: 0.7;
}

/* HEADER */
header {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 30px 40px 20px 40px;
  gap: 20px;
}

.logo img {
  height: 48px;
  display: block;
}

/* NAVIGATION ICONS */
.nav {
  display: flex;
  justify-content: center;
  gap: 25px;
}

.nav-icon {
  position: relative;
  width: 46px;
  height: 46px;
  border: none;
  border-radius: 50%;
  border: 2px solid #000000;
  background-color: #D9F74A;
  display: flex;
  justify-content: center;
  align-items: center;
  cursor: pointer;
  transition: background-color 0.3s, transform 0.2s;
}

.nav-icon img {
  width: 24px;
  height: 24px;
}

.nav-icon:hover {
  background-color: #00C853;
  transform: scale(1.05);
}

.nav-icon:hover img {
  filter: brightness(100) invert(1);
}

.nav-icon::after {
  content: attr(data-tooltip);
  position: absolute;
  bottom: -38px;
  left: 50%;
  transform: translateX(-50%);
  background-color: #00B0FF;
  color: #fff;
  padding: 6px 10px;
  border-radius: 5px;
  font-size: 13px;
  white-space: nowrap;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s ease-in-out, transform 0.2s;
}

.nav-icon:hover::after {
  opacity: 1;
  transform: translateX(-50%) translateY(4px);
}

/* RESPONSIVE HEADER */
@media (max-width: 768px) {
  header {
    gap: 15px;
    padding: 20px;
  }

  .nav {
    flex: none;
  }
}

/* ERROR MESSAGE */
.error {
  color: #ff0000;
  font-weight: bold;
}