#auth-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: #0f172a; /* Slate 900 */
    z-index: 9999;
    display: none;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: opacity 0.3s ease;
    backdrop-filter: blur(5px);
}

#auth-overlay.active {
    display: flex;
    opacity: 1;
}

.auth-card {
    background: #1e293b; /* Slate 800 */
    padding: 2.5rem;
    border-radius: 1rem;
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
    width: 90%;
    max-width: 400px;
    text-align: center;
    border: 1px solid #334155;
    position: relative; /* For absolute positioning of language switcher */
}

.auth-lang-switcher {
    position: absolute;
    top: 1.5rem;
    right: 1.5rem;
    display: flex;
    gap: 8px;
    align-items: center;
}

.auth-lang-switcher .lang-btn {
    background: none;
    border: none;
    color: #64748b;
    font-weight: 600;
    font-size: 0.875rem;
    cursor: pointer;
    padding: 0;
    transition: color 0.2s;
}

.auth-lang-switcher .lang-btn:hover {
    color: #94a3b8;
}

.auth-lang-switcher .lang-btn.active {
    color: #3b82f6;
}

.auth-lang-switcher .divider {
    color: #334155;
    font-size: 0.875rem;
}

.auth-icon {
    width: 64px;
    height: 64px;
    background: linear-gradient(135deg, #3b82f6, #2563eb);
    border-radius: 16px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 1.5rem;
    box-shadow: 0 10px 25px -5px rgba(37, 99, 235, 0.4);
}

.auth-icon i {
    font-size: 32px;
    color: white;
}

.auth-title {
    color: #f8fafc;
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.auth-subtitle {
    color: #94a3b8;
    font-size: 0.875rem;
    margin-bottom: 2rem;
    line-height: 1.5;
}

.auth-input-group {
    margin-bottom: 1.5rem;
    text-align: left;
}

.auth-input {
    width: 100%;
    padding: 0.875rem 1rem;
    background: #0f172a;
    border: 1px solid #334155;
    border-radius: 0.5rem;
    color: #fff;
    font-size: 1rem;
    transition: all 0.2s;
    box-sizing: border-box;
}

.auth-input:focus {
    outline: none;
    border-color: #3b82f6;
    box-shadow: 0 0 0 2px rgba(59, 130, 246, 0.2);
}

.auth-btn {
    width: 100%;
    padding: 0.875rem;
    background: #3b82f6;
    color: white;
    border: none;
    border-radius: 0.5rem;
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: background 0.2s;
}

.auth-btn:hover {
    background: #2563eb;
}

.auth-error {
    color: #ef4444;
    font-size: 0.875rem;
    margin-top: 1rem;
    display: none;
    padding: 0.5rem;
    background: rgba(239, 68, 68, 0.1);
    border-radius: 0.375rem;
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    10%, 30%, 50%, 70%, 90% { transform: translateX(-5px); }
    20%, 40%, 60%, 80% { transform: translateX(5px); }
}

.auth-input.shake {
    animation: shake 0.4s cubic-bezier(.36,.07,.19,.97) both;
    border-color: #ef4444;
}