:root {
    /* Dark Theme (default) */
    --bg-color: #1c2526; /* Matte metallic dark */
    --text-color: #ffffff;
    --header-bg: #2c2c2c;
    --section-bg: #2c2c2c;
    --button-start: #00b4d8;
    --button-end: #0096c7;
    --accent-color: #90e0ef;
    --shadow-color: rgba(0, 0, 0, 0.5);
}

[data-theme="light"] {
    --bg-color: #e0e0e0; /* Light metallic */
    --text-color: #333333;
    --header-bg: #f0f0f0;
    --section-bg: #f0f0f0;
    --button-start: #0077b6;
    --button-end: #023e8a;
    --accent-color: #0077b6;
    --shadow-color: rgba(0, 0, 0, 0.2);
}

[data-theme="neon"] {
    --bg-color: #0d0d0d; /* Deep black for glow pop */
    --text-color: #00ffcc;
    --header-bg: #1a1a1a;
    --section-bg: #1a1a1a;
    --button-start: #ff0066;
    --button-end: #ffcc00;
    --accent-color: #00ffcc;
    --shadow-color: rgba(255, 0, 102, 0.5);
}

body {
    font-family: 'Segoe UI', Arial, sans-serif;
    background: 
        linear-gradient(90deg, rgba(0, 180, 216, 0.1) 1px, transparent 1px),
        linear-gradient(0deg, rgba(0, 180, 216, 0.1) 1px, transparent 1px),
        radial-gradient(circle at 20% 30%, rgba(0, 180, 216, 0.3) 0%, transparent 10%),
        radial-gradient(circle at 70% 60%, rgba(255, 107, 107, 0.25) 0%, transparent 8%),
        radial-gradient(circle at 40% 80%, rgba(155, 89, 182, 0.2) 0%, transparent 6%),
        radial-gradient(circle at 50% 50%, transparent 50%, rgba(0, 0, 0, 0.4) 80%),
        linear-gradient(135deg, var(--bg-color), #2a3435, var(--bg-color));
    background-size: 
        50px 50px, 50px 50px,
        100% 100%, 100% 100%, 100% 100%,
        100% 100%,
        100% 100%;
    background-position: center;
    background-repeat: repeat, repeat, no-repeat, no-repeat, no-repeat, no-repeat, no-repeat;
    animation: gridPulse 6s infinite ease-in-out;
    color: var(--text-color);
    margin: 0;
    padding: 20px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

h1 {
    margin: 0 0 20px;
    font-size: 24px;
    color: var(--button-start);
    text-align: center;
}

form {
    background-color: var(--section-bg);
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 4px 10px var(--shadow-color);
    text-align: center;
    max-width: 400px;
    width: 100%;
}

input[type="text"],
input[type="password"] {
    display: block;
    width: calc(100% - 20px);
    padding: 10px;
    margin: 10px auto;
    border: 1px solid var(--accent-color);
    border-radius: 5px;
    background-color: var(--section-bg);
    color: var(--text-color);
    font-size: 14px;
}

input[type="text"]:focus,
input[type="password"]:focus {
    outline: none;
    border-color: var(--button-start);
    box-shadow: 0 0 5px var(--button-start);
}

button {
    background: linear-gradient(45deg, var(--button-start), var(--button-end));
    border: none;
    padding: 10px 20px;
    color: var(--text-color);
    font-size: 14px;
    border-radius: 5px;
    cursor: pointer;
    box-shadow: 0 0 5px var(--button-start);
    transition: all 0.3s ease;
    width: 100%;
    margin-top: 10px;
}

button:hover {
    transform: scale(1.05);
    box-shadow: 0 0 10px var(--button-start);
}

button:active {
    animation: bounce 0.2s;
}

@keyframes gridPulse {
    0%, 100% { opacity: 0.8; }
    50% { opacity: 1; }
}

@keyframes bounce {
    0% { transform: scale(1); }
    50% { transform: scale(0.95); }
    100% { transform: scale(1); }
}

@media (max-width: 600px) {
    form {
        padding: 15px;
        max-width: 90%;
    }
    h1 { font-size: 20px; }
}