:root {
    --neon-green: #39ff14;
    --light-bg: #ffffff;
    --dark-bg: #121212;
    --light-text: #333333;
    --dark-text: #ffffff;
}

body {
    margin: 0;
    padding: 0;
    min-height: 100vh;
    padding-top: 80px;
    transition: all 0.3s ease;
    overflow-x: hidden;
}

body.light-theme {
    background-color: var(--light-bg);
    color: var(--light-text);
}

body.dark-theme {
    background-color: var(--dark-bg);
    color: var(--dark-text);
}

#particles-js {
    position: fixed;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    z-index: 1;
    opacity: 0.6;
}

.navbar {
    backdrop-filter: blur(10px);
    padding: 1rem 0;
    z-index: 1000;
    background: rgba(255, 255, 255, 0.1);
}

.neon-text {
    color: var(--neon-green);
    text-shadow: 0 0 5px var(--neon-green),
                 0 0 10px var(--neon-green),
                 0 0 20px var(--neon-green);
    animation: neon-pulse 1.5s infinite alternate;
    font-size: 1.8rem;
}

.theme-toggle {
    background: none;
    border: none;
    color: var(--neon-green);
    font-size: 1.5rem;
    cursor: pointer;
    transition: all 0.3s ease;
    padding: 8px;
    border-radius: 50%;
    width: 45px;
    height: 45px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-toggle:hover {
    transform: scale(1.1);
    text-shadow: 0 0 10px var(--neon-green);
}

.theme-toggle i {
    transition: all 0.3s ease;
}

main {
    position: relative;
    z-index: 2;
    padding: 2rem;
}

.language-card {
    perspective: 1000px;
    height: 300px;
    margin-bottom: 30px;
}

.card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    text-align: center;
    transition: transform 0.8s;
    transform-style: preserve-3d;
    cursor: pointer;
}

.language-card:hover .card-inner {
    transform: rotateY(180deg);
}

.card-front, .card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(5px);
    border: 2px solid var(--neon-green);
    border-radius: 15px;
    padding: 20px;
    box-shadow: 0 0 15px rgba(57, 255, 20, 0.2);
    transition: all 0.3s ease;
}

.card-front:hover, .card-back:hover {
    box-shadow: 0 0 25px rgba(57, 255, 20, 0.4);
}

.card-back {
    transform: rotateY(180deg);
    background: rgba(0, 0, 0, 0.8);
}

.language-logo {
    width: 80px;
    height: 80px;
    margin-bottom: 1rem;
    filter: drop-shadow(0 0 5px rgba(57, 255, 20, 0.5));
    transition: all 0.3s ease;
}

.language-card:hover .language-logo {
    transform: scale(1.1);
    filter: drop-shadow(0 0 10px rgba(57, 255, 20, 0.8));
}

.language-description {
    font-size: 0.9rem;
    margin-top: 0.5rem;
    padding: 0 1rem;
}

.dark-theme .language-description {
    color: var(--dark-text);
}

.light-theme .language-description {
    color: var(--light-text);
}

h2 {
    color: var(--neon-green);
    margin-top: 0.5rem;
    font-size: 1.5rem;
    text-shadow: 0 0 5px var(--neon-green);
}

.start-btn {
    background: var(--neon-green);
    border: none;
    padding: 10px 30px;
    border-radius: 25px;
    color: black;
    font-weight: bold;
    text-decoration: none;
    cursor: pointer;
    transition: all 0.3s ease;
    margin-top: 1rem;
    display: inline-block;
}

.start-btn:hover {
    transform: scale(1.1);
    box-shadow: 0 0 15px var(--neon-green);
}

@keyframes neon-pulse {
    from {
        text-shadow: 0 0 5px var(--neon-green),
                     0 0 10px var(--neon-green),
                     0 0 20px var(--neon-green);
    }
    to {
        text-shadow: 0 0 2px var(--neon-green),
                     0 0 5px var(--neon-green),
                     0 0 10px var(--neon-green);
    }
}

@media (max-width: 768px) {
    .language-card {
        height: 250px;
    }

    .language-logo {
        width: 60px;
        height: 60px;
    }

    .language-description {
        font-size: 0.8rem;
    }
}