* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: system-ui, sans-serif;
            color: #222;
            background: #fff;
            line-height: 1.6;
        }

        header {
            border-bottom: 1px solid #e5e5e5;
        }

        nav {
            max-width: 1000px;
            margin: 0 auto;
            padding: 1.25rem;
            display: flex;
            justify-content: space-between;
            align-items: center;
        }

        nav ul {
            display: flex;
            gap: 2rem;
            list-style: none;
        }

        nav a {
            text-decoration: none;
            color: #222;
        }

        nav a:hover {
            color: #666;
        }

        main {
            max-width: 1000px;
            margin: 0 auto;
            padding: 8rem 1.25rem;
        }

        h1 {
            font-size: 3rem;
            font-weight: 600;
            margin-bottom: 1rem;
        }

        p {
            max-width: 650px;
            color: #555;
            font-size: 1.1rem;
        }

        .button {
            display: inline-block;
            margin-top: 2rem;
            padding: 0.8rem 1.4rem;
            border: 1px solid #222;
            text-decoration: none;
            color: #222;
        }

        .button:hover {
            background: #222;
            color: #fff;
        }

        footer {
            border-top: 1px solid #e5e5e5;
            text-align: center;
            padding: 2rem;
            color: #777;
        }
        footer a {
    color: inherit;
    text-decoration: none;
}

footer a:hover {
    text-decoration: underline;
}
        

.button {
    display: inline-block;
    padding: 0.75rem 1.25rem;
    border: 1px solid #222;
    text-decoration: none;
    color: #222;
}

.button:hover {
    background: #222;
    color: #fff;
}



.tense-overview {
    margin-top: 2rem;
}

.tense-accordion {
    border-bottom: 1px solid #e5e7eb;
}

.tense-accordion[open] {
    margin-bottom: 1.5rem;
}

.tense-accordion summary {
    position: relative;
    background: #fafafa;

    display: grid;
    grid-template-columns: 1.2fr 1fr 2fr;
    gap: 1rem;

    padding: 0.75rem 3rem 0.75rem 1rem;
}

.tense-accordion summary::-webkit-details-marker {
    display: none;
}

.tense-accordion summary:hover {
    background: #f9fafb;
}

.tense-accordion summary span:first-child {
    font-weight: 600;
}

.tense-accordion summary::after {
    content: "+";

    position: absolute;
    right: 1rem;
    top: 50%;

    transform: translateY(-50%);

    font-size: 1.2rem;
    font-weight: bold;
}

.tense-accordion[open] summary::after {
    content: "−";
}

.tense-title {
    grid-column: 1 / -1;
    font-weight: 700;
}

.tense-detail {
    padding: 0.75rem 1rem;
    background: #fafafa;
    /*border: 1px solid #e5e7eb;*/
    border-top: none;
    border-radius: 0 0 12px 12px;
}

.tense-detail p {
    margin: 0.4rem 0;
}
.flashcards {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;

    margin-top: 3rem;
}

.flashcard {
    width: 100%;
    height: 450px;
}

.flashcard-inner {
    position: relative;

    width: 100%;
    height: 100%;

    transition: transform 0.6s;
    transform-style: preserve-3d;

    cursor: pointer;
}

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

.flashcard-front,
.flashcard-back {
    position: absolute;

    width: 100%;
    height: 100%;

    backface-visibility: hidden;

    border: 1px solid #e5e7eb;
    border-radius: 12px;

    padding: 2rem;

    background: white;
}

.flashcard-front {
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 0;
    text-align: center;
}

.flashcard-back {
    transform: rotateY(180deg);
}

.flashcard-front h2 {
    margin: 0;
}

.flashcard-back h3 {
    margin-top: 1rem;
    margin-bottom: 0.5rem;

    font-size: 0.9rem;
    color: #6b7280;
}

.flashcard-back ul {
    margin-left: 1.25rem;
}

.flashcard-back li {
    font-family: system-ui, sans-serif;
    color: #555;
    font-size: 1.1rem;
    line-height: 1.6;
}

.tense-accordion[open] .tense-detail {
    margin-bottom: 1.5rem !important;
}


@media (min-width: 768px) {

    .flashcards {
        grid-template-columns: repeat(2, 1fr);
    }

}

@media (min-width: 1200px) {

    .flashcards {
        grid-template-columns: repeat(3, 1fr);
    }
    .flashcard {
    
    height: 500px;
}

}