* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: Arial, sans-serif;
}

body {
    background-color: #f5f5f5;
    color: #000; 
    line-height: 2.0;
}

/* Header */
header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.3rem 3rem; 
    background-color: #fff;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

.logo img {
    width: 3rem; 
    height: auto;
    display: block;
}

/* Header-navigation */
nav ul {
    list-style: none;
    display: flex;
    justify-content: flex-end;
}

nav ul li a {
    text-decoration: none;
    color: #000; 
    margin-bottom: 0;
    display: inline-block;
    position: relative;
    padding: 8px 15px;  
    font-weight:bold;  
}

nav ul li a:hover {
    background-color: rgba(0, 0, 0, 0.1); 
    z-index: 1;
}

/* Header-navigation-dropdown */
.dropdown {
    position: relative;
}

.dropdown-menu {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    background-color: #fff;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
    list-style: none;
    padding: 0;
    margin: 0;
}

.dropdown-menu li a {
    display: block;
    padding: 8px 15px;
    text-decoration: none;
    color: #000;
}

.dropdown-menu li a:hover {
    background-color: rgba(0, 0, 0, 0.1);
}

.dropdown:hover .dropdown-menu {
    display: block;
}

/* Hero Section */
.hero {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 3rem;
    min-height: 12rem; 
    background-image: url('hero.jpeg');
    background-size: cover;
    background-position: center;
    background-attachment: fixed;
    background-repeat: no-repeat;
}

.hero-text h1 {
    color: #ffffff;
    text-align: center;
    font-size: 3rem; 
    line-height: 1.2;
    font-weight: bold;
}

/* Student ID Section */
.sid {
    background-color: #fff;
    color: #000;
    padding: 1.5rem 3rem;
}

.sid p {
    margin-bottom: 0.5rem;
    font-size: 0.875rem; 
}

/* Content Section */
.content {
    max-width: 50rem; 
    margin: 0 auto;
    padding: 1.5rem 3rem;
}

.content h2 {
    font-size: 1.8rem;
    margin-top: 1.5rem;
    color: #000;
}

.content p {
    margin-bottom: 1rem;
    color: #000;
}

/* Footer-references Section */
footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.3rem 3rem; 
    background-color: #fff;
}

.references h3 {
    font-size: 1.2em;
    margin-bottom: 10px;
    color: #333;
}

.references li {
    list-style: none; 
    padding: 0;
    font-size: 1em;
    margin-bottom: 3px; 
    text-indent: -0.5in; 
    padding-left: 0.5in; 
}



/* Bottom navigation for button */
.Bottom-navigation {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px;
    background-color: #f4f4f4;
    border-top: 1px solid #ddd;
    position: sticky;
    bottom: 0;
    width: 100%;
}

.Bottom-nav_button {
    text-decoration: none;
    color: #333;
    font-weight: bold;
    padding: 10px 20px;
    border: 2px solid #333;
    border-radius: 5px;
    transition: background-color 0.3s, color 0.3s;
}

.Bottom-nav_button:hover {
    background-color: #333;
    color: #fff;
}

.previous {
    margin-left: 20px;
}

.next {
    margin-right: 20px;
    margin-left: auto;
}


/* Content of Blockchain Architecture Section */
.content-Architecture {
    max-width: 50rem; 
    margin: 0 auto;
    padding: 1.5rem 3rem;
    
}

.content-Architecture::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image:url('hero.jpeg');
    opacity: 0.1; 
    z-index: -1; 
}

.content-Architecture h2 {
    font-size: 1.8rem;
    margin-top: 1.5rem;
    color: #000;
}

.content-Architecture p {
    margin-bottom: 1rem;
    color: #000;
    font-size: 1rem;

}


/* Content of Consensus Mechanisms Section */
.content-Consensus_Mechanisms {
    max-width: 50rem; 
    margin: 0 auto;
    padding: 1.5rem 3rem;
    
}

.content-Consensus_Mechanisms::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image:url('hero.jpeg');
    opacity: 0.1; 
    z-index: -1; 
}

.content-Consensus_Mechanisms h2 {
    font-size: 1.8rem;
    margin-top: 1.5rem;
    color: #000;
}

.content-Consensus_Mechanisms p {
    margin-bottom: 1rem;
    color: #000;
    font-size: 1rem;
}


/* quiz */
.hidden {
    display: none;
}

#question-container {
    padding: 20px;
    border: 1px solid #ddd;
    border-radius: 5px;
}

.option-btn {
    padding: 10px 15px;
    margin: 5px;
    cursor: pointer;
    border: 1px solid #ccc;
    border-radius: 4px;
    background-color: #f9f9f9;
}
.option-btn.selected {
    background-color: #d3e4ff;
}

#result-container {
    padding: 20px;
    border: 1px solid #ddd;
    border-radius: 5px;
    background-color: #fff;
}

.progress-bar {
    width: 100%;
    height: 20px;
    background-color: #f0f0f0;
    padding: 5px;
    border-radius: 5px;
}
#progress-fill {
    height: 100%;
    background-color: #4caf50;
    width: 0;
    transition: width 0.3s;
    border-radius: 3px;
}

#question {
    padding: 10px 0;
    font-size: 1.5em;
}

#progress {
    padding: 10px 0;
    font-size: 1em;
}

.correct-answer {
    color: green;
}

#result-feedback {
    padding: 15px;
}
#result-feedback li {
    padding: 10px 0;
}