body {
    background-color: #1b1f22;
}

.nav {
    background-color: #8155e9;
}

.navbar-brand:hover,
.navbar-brand:focus {
    color: #fff;
    text-decoration: none;
}


/* Navbar logo */
#logo {
    height: 70px;           
    width: auto;            
    margin-right: 0.5rem;   
    border-radius: 8px;  
}


#logo:hover {
    transform: scale(1.05);
}

/* Navbar buttons */
.btn-check + label.btn {
    color: #f8f9fa; 
    background-color: #6c5ce7;
    border: 2px solid #ffffff50;
    transition: background-color 0.3s, transform 0.2s;
}

.btn-check:checked + label.btn {
    background-color: #d0a7ff; 
    color: #2d3436; 
    border-color: #fff;
}

/* hover */
.btn-check + label.btn:hover {
    background-color: #a29bfe;
    transform: scale(1.05);
}


/* Section default hidden */
section {
    display: none;
    padding: 2rem;
}

section.active {
    display: block;
}

/* Card styling */
.card {
    border-radius: 12px;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.card:hover {
    transform: translateY(-3px);
    box-shadow: 0 6px 12px rgba(0, 0, 0, 0.15);
}


/* Button styling */
.btn {
    border-radius: 20px;
    font-size: 0.9rem;
}

/* Section paragraph style */
#library p,
#learn p,
#author p {
    font-style: italic;
    color: #6c757d;
}

/* Capsule container */
.capsule {
    border-radius: 20px;
}

/* Placeholder styling */
::placeholder {
    color: #aaa !important;
    opacity: 1;
}

::-webkit-input-placeholder {
    color: #aaa !important;
    opacity: 1;
}

:-moz-placeholder {
    color: #aaa !important;
    opacity: 1;
}

::-moz-placeholder {
    color: #aaa !important;
    opacity: 1;
}

:-ms-input-placeholder {
    color: #aaa !important;
    opacity: 1;
}

/* Progress bar gradient */
.progress-bar {
    background: linear-gradient(90deg, rgba(125, 178, 240, 1) 0%, rgba(119, 119, 242, 1) 35%, rgba(237, 135, 179, 1) 100%);
}

/* Flashcard container */
#flashBox {
    width: 100%;
    max-width: 400px;
    height: 200px;
    perspective: 1000px;
    margin: 0 auto;
}

/* Flashcard inner (3D flip) */
.card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    transition: transform 0.6s;
    transform-style: preserve-3d;
}

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

/* Flashcard faces */
.card-front,
.card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    border: 2px solid #0dcaf0;
    border-radius: 1rem;
    padding: 1rem;
    box-sizing: border-box;
}

.card-front {
    background-color: #212529;
    color: #f8f9fa;
}

.card-back {
    background-color: #0dcaf0;
    color: #212529;
    transform: rotateY(180deg);
}