html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', sans-serif;
    background-color: #0a0a0a;
    color: #e5e7eb;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 1rem;
    margin: 0;
}
        
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-image: 
        radial-gradient(circle at 15% 80%, rgba(79, 70, 229, 0.2), transparent 40%),
        radial-gradient(circle at 85% 25%, rgba(59, 130, 246, 0.15), transparent 40%);
    filter: blur(80px);
    z-index: -1;
    pointer-events: none;
}

.main-container {
    position: relative;
    z-index: 1;
    width: 100%;
    max-width: 42rem; /* 672px */
    margin-left: auto;
    margin-right: auto;
}

.header {
    text-align: center;
    margin-bottom: 2.5rem;
}

.title {
    font-size: 2.25rem; /* 36px */
    line-height: 2.5rem; /* 40px */
    font-weight: 900;
    color: #fff;
    letter-spacing: -0.025em;
}

.subtitle {
    color: #9ca3af;
    margin-top: 0.75rem;
    font-size: 1.125rem; /* 18px */
    line-height: 1.75rem; /* 28px */
}

.deck-container {
    margin-bottom: 2rem;
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 1rem;
}

.flashcard-container {
    perspective: 2000px;
    width: 100%;
    height: 20rem; /* 320px */
    margin-bottom: 2rem;
}
@media (min-width: 768px) {
    .flashcard-container {
        height: 24rem; /* 384px */
    }
}


.flashcard {
    width: 100%;
    height: 100%;
    position: relative;
    transition: transform 0.6s cubic-bezier(0.25, 0.46, 0.45, 0.94); /* Ajuste no tempo da animação do flashcard, nao mexer, tempo ja esta ideal */
    transform-style: preserve-3d;
}

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

.flashcard-face {
    position: absolute;
    width: 100%;
    height: 100%;
    -webkit-backface-visibility: hidden;
    backface-visibility: hidden;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    padding: 2.5rem;
    text-align: center;
    border-radius: 1.5rem;
    border: 1px solid rgba(255, 255, 255, 0.1);
    

    background: rgba(30, 41, 59, 0.6); 
    
    box-shadow: 0 0 40px rgba(0,0,0,0.2);
}

.card-text-front {
    font-size: 1.25rem; /* 20px */
    font-weight: 700;
    color: #fff;
}
@media (min-width: 768px) {
    .card-text-front {
        font-size: 1.5rem; /* 24px */
    }
}

.card-text-back {
    font-size: 1rem; /* 16px */
    font-weight: 500;
    color: #d1d5db;
}
@media (min-width: 768px) {
    .card-text-back {
        font-size: 1.125rem; /* 18px */
    }
}


.flashcard-front::before, .flashcard-back::before {
    content: 'PERGUNTA';
    position: absolute;
    top: 1.5rem;
    font-size: 0.75rem;
    font-weight: 600;
    letter-spacing: 0.1em;
}

.flashcard-front::before {
    color: #6b7280;
}

.flashcard-back {
    transform: rotateY(180deg);
    background: rgba(49, 46, 129, 0.5); 
}

.flashcard-back::before {
    content: 'RESPOSTA';
    color: #9ca3af;
}

.card-counter {
    text-align: center;
    color: #6b7280;
    margin-bottom: 1.5rem;
    font-weight: 600;
}
        
.deck-button, .nav-button, .flip-button {
    transition: all 0.3s ease;
    border: 1px solid rgba(255, 255, 255, 0.1);
    box-shadow: 0 4px 6px rgba(0,0,0,0.2);
    cursor: pointer;
}

.deck-button {
    background: rgba(55, 65, 81, 0.7);
    color: white;
    font-weight: 600;
    padding: 0.75rem 1.5rem;
    border-radius: 9999px;
}

.deck-button:hover, .nav-button:hover, .flip-button:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 15px rgba(0,0,0,0.2);
}

.deck-button.active {
    background-color: #4f46e5;
    color: white;
    border-color: #4f46e5;
    box-shadow: 0 0 20px rgba(79, 70, 229, 0.5);
}

.nav-container {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1.5rem;
}

.nav-button {
    background: rgba(55, 65, 81, 0.7);
    padding: 1rem;
    border-radius: 9999px;
    color: #d1d5db;
    width: 56px;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.flip-button {
    background: linear-gradient(45deg, #4f46e5, #3b82f6);
    color: white;
    font-weight: 700;
    padding: 1rem 2.5rem;
    border-radius: 9999px;
    font-size: 1.125rem; /* 18px */
    box-shadow: 0 4px 6px rgba(0,0,0,0.2);
}

.footer {
    position: relative;
    margin-top: 2.5rem;
    text-align: center;
    color: #4b5563;
    font-size: 0.875rem; /* 14px */
    width: 100%;
}

.card-text-front, .card-text-back {
    transition: opacity 0.15s ease-in-out;
}

.flashcard-container.is-loading .card-text-front,
.flashcard-container.is-loading .card-text-back {
    opacity: 0;
}