@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@300;400;600&display=swap');

:root {
    --bg-dark: #121212;
    --primary: #1a1a1a;
    --text: #e0e0e0;
    --accent1: #bb86fc;
    --accent2: #03dac6;
    --surface: #1e1e1e;
    --shadow-color: rgba(0, 0, 0, 0.5);
}

body {
    font-family: 'Poppins', sans-serif;
    line-height: 1.7;
    margin: 0;
    padding: 0;
    background: var(--bg-dark);
    color: var(--text);
}

header {
    background: var(--primary);
    color: var(--accent1);
    padding: 2rem 1rem;
    text-align: center;
    border-bottom: 2px solid var(--accent2);
}

header h1 {
    margin: 0 0 0.5rem 0;
    font-size: 2.2rem;
}

header p {
    margin: 0;
    font-size: 1.1rem;
    color: var(--text);
    opacity: 0.8;
}

nav a.home-link {
    display: inline-block;
    margin-top: 1.5rem;
    color: var(--accent2);
    text-decoration: none;
    padding: 0.5rem 1rem;
    border: 1px solid var(--accent2);
    border-radius: 20px;
    transition: all 0.3s ease;
}

nav a.home-link:hover {
    background: var(--accent2);
    color: var(--bg-dark);
}

main {
    padding: 2rem 1rem;
    max-width: 900px;
    margin: 0 auto;
}

section {
    background: var(--surface);
    padding: 2rem;
    margin-bottom: 2rem;
    border-radius: 15px;
    box-shadow: 0 5px 15px var(--shadow-color);
}

h2 {
    color: var(--accent1);
    text-align: center;
    font-size: 1.8rem;
    margin-top: 0;
    margin-bottom: 2rem;
}

/* Card Container */
.card-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    perspective: 1000px;
}

.card {
    background-color: transparent;
    height: 220px;
    cursor: pointer;
}

.card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    text-align: center;
    transition: transform 0.6s;
    transform-style: preserve-3d;
}

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

.card-front, .card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    -webkit-backface-visibility: hidden;
    backface-visibility: hidden;
    border-radius: 10px;
    padding: 1.5rem;
    box-sizing: border-box;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.card-front {
    background: var(--primary);
    border: 1px solid var(--accent1);
}

.card-front h3 {
    color: var(--accent1);
    margin-top: 0;
}

.card-back {
    background: var(--accent1);
    color: var(--bg-dark);
    transform: rotateY(180deg);
}

.card-back h4 {
    margin-top: 0;
}
.card-back ul {
    list-style-type: none;
    padding: 0;
    margin: 0;
    text-align: left;
}
.card-back li {
    margin-bottom: 0.5rem;
}


/* Exercises Section */
.exercise {
    margin-bottom: 2rem;
    padding: 1.5rem;
    background: var(--primary);
    border-radius: 10px;
}

.exercise h3 {
    color: var(--accent2);
    margin-top: 0;
}

audio {
    width: 100%;
    margin-top: 1rem;
    filter: invert(1) hue-rotate(180deg);
}

footer {
    text-align: center;
    padding: 2rem 1rem;
    background: var(--primary);
    color: var(--text);
    opacity: 0.7;
}