header {
    width: 100%;
    background-color: var(--color-white);
    padding: var(--spacing-20) 0;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-20);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

/* Left-header: logo and navigation menu grouping */
.left-header {
    display: flex;
    align-items: center;
    gap: 40px;
}

.logo img {
    height: 40px;
}

.nav-menu {
    list-style: none;
    display: flex;
    gap: 65px;
}

.nav-menu li a {
    text-decoration: none;
    color: var(--color-text-gray);
    font-weight: 600;
    font-size: var(--font-size-base);
    transition: text-shadow var(--transition-duration) var(--transition-timing), color var(--transition-duration) var(--transition-timing);
}

.nav-menu li a:hover {
    color: var(--color-white);
    animation: glowText 2s infinite alternate;
}

@keyframes glowText {
  0% {
    text-shadow: 0 0 5px var(--color-blue), 0 0 10px var(--color-blue), 0 0 15px var(--color-purple), 0 0 20px var(--color-purple);
  }
  50% {
    text-shadow: 0 0 5px var(--color-purple), 0 0 10px var(--color-purple), 0 0 15px var(--color-blue), 0 0 20px var(--color-blue);
  }
  100% {
    text-shadow: 0 0 5px var(--color-blue), 0 0 10px var(--color-blue), 0 0 15px var(--color-purple), 0 0 20px var(--color-purple);
  }
}

/* Login and Sign In Area */
.login-signup {
    display: flex;
    align-items: center;
    gap: var(--spacing-20);
}

/* Login link */
.login {
    display: flex;
    align-items: center;
    gap: 8px;
    text-decoration: none;
    color: var(--color-purple);
    font-weight: 600;
    font-size: var(--font-size-base);
}

.login img {
    width: 20px;
    height: 20px;
}

.login:hover {
    text-decoration: none;
}

.login span {
    transition: text-shadow var(--transition-duration) var(--transition-timing), color var(--transition-duration) var(--transition-timing);
}

.login:hover span {
    color: var(--color-white);
    animation: glowText 2s infinite alternate;
}

/* Glowing Sign In button */
.glow-on-hover {
    position: relative;
    z-index: 0;
    display: inline-block;
    padding: 8px 20px;
    font-weight: 600;
    text-decoration: none;
    border-radius: var(--border-radius);
    font-size: var(--font-size-base);
    cursor: pointer;
    color: var(--color-blue);
    border: 0.01px solid var(--color-blue);
    background-color: var(--color-white);
    transition: background-color var(--transition-duration) var(--transition-timing), color var(--transition-duration) var(--transition-timing);
}

.glow-on-hover:before {
    content: '';
    position: absolute;
    top: -2px;
    left: -2px;
    width: calc(100% + 4px);
    height: calc(100% + 4px);
    background: linear-gradient(var(--gradient-angle), var(--color-purple), var(--color-blue), var(--color-purple));
    background-size: 400%;
    filter: blur(5px);
    opacity: 0;
    transition: opacity var(--transition-duration) var(--transition-timing);
    border-radius: var(--border-radius);
    z-index: -2;
    animation: glowing 20s linear infinite;
}

.glow-on-hover:hover:before {
    opacity: 1;
}

.glow-on-hover:after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--color-white);
    border-radius: var(--border-radius);
    z-index: -1;
    transition: background-color var(--transition-duration) var(--transition-timing);
}

.glow-on-hover:active:after {
    background: linear-gradient(var(--gradient-angle), var(--color-purple), var(--color-blue), var(--color-purple));
}

.glow-on-hover:active {
    color: var(--color-white);
}

@keyframes glowing {
    0% { background-position: 0 0; }
    50% { background-position: 400% 0; }
    100% { background-position: 0 0; }
}