/* ETDA Style Variables */
:root {
    --color-primary: #3FBE4B;
    --color-primary-dark: rgb(0, 138, 68);
    --color-text-main: rgb(51, 51, 51);
    --color-text-light: #FFFFFF;
    --color-bg-body: #F5F7FA;
    /* Light gray background for contrast with white cards */
    --color-bg-card: #FFFFFF;
    --font-family-main: 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', 'Segoe UI', sans-serif;
    --border-radius-card: 16px;
    --box-shadow-card: 0 4px 6px rgba(0, 0, 0, 0.05), 0 1px 3px rgba(0, 0, 0, 0.1);
    --spacing-section: 3rem;
}

body {
    font-family: var(--font-family-main);
    color: var(--color-text-main);
    background-color: var(--color-bg-body);
    line-height: 1.6;
    margin: 0;
    padding: 0;
}

h1,
h2,
h3,
h4 {
    font-weight: 700;
    margin-bottom: 1rem;
}

h1 {
    font-size: 2.5rem;
    color: var(--color-text-light);
}

h2 {
    font-size: 2rem;
    color: var(--color-primary);
    text-align: center;
    margin-top: 2rem;
}

h3 {
    font-size: 1.5rem;
    color: var(--color-primary-dark);
    margin-top: 1.5rem;
}

h4 {
    font-size: 1.25rem;
    color: var(--color-text-main);
    font-weight: 600;
    margin-top: 1rem;
}

a {
    color: var(--color-primary);
    text-decoration: none;
    transition: color 0.3s ease;
}

a:hover {
    color: var(--color-primary-dark);
}

/* Header & Nav */
header {
    background-color: white;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    position: sticky;
    top: 0;
    z-index: 1000;
    padding: 1rem 0;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo-img {
    height: 50px;
    /* Adjust based on logo aspect ratio */
    width: auto;
}

nav ul {
    list-style: none;
    display: flex;
    gap: 2rem;
    margin: 0;
    padding: 0;
}

nav a {
    color: var(--color-text-main);
    font-weight: 500;
    font-size: 1rem;
}

nav a:hover,
nav a.active {
    color: var(--color-primary);
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--color-primary-dark) 0%, var(--color-primary) 100%);
    color: white;
    padding: 4rem 1.5rem;
    text-align: center;
    margin-bottom: var(--spacing-section);
}

.hero p {
    font-size: 1.25rem;
    opacity: 0.9;
    max-width: 800px;
    margin: 1rem auto 0;
}

/* Main Layout */
.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 0 1.5rem;
    padding-bottom: 4rem;
}

/* Cards */
.card {
    background-color: var(--color-bg-card);
    border-radius: var(--border-radius-card);
    box-shadow: var(--box-shadow-card);
    padding: 2.5rem;
    margin-bottom: 2rem;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.card:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 15px rgba(0, 0, 0, 0.05);
}

/* Tables */
table {
    width: 100%;
    border-collapse: collapse;
    margin: 1.5rem 0;
    font-size: 0.95rem;
}

th,
td {
    padding: 1rem;
    border-bottom: 1px solid #eee;
    text-align: left;
}

th {
    background-color: aliceblue;
    /* Very light blue/gray */
    color: var(--color-primary-dark);
    font-weight: 600;
}

/* Exercises Module */
.exercises-section {
    margin-top: 4rem;
}

.exercise-item {
    background: white;
    border: 1px solid #eee;
    border-radius: 12px;
    padding: 2rem;
    margin-bottom: 2rem;
}

.exercise-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 1rem;
}

.badge {
    background-color: var(--color-primary);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: bold;
    text-transform: uppercase;
}

.btn-toggle {
    background-color: var(--color-primary);
    color: white;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: 30px;
    cursor: pointer;
    font-weight: 600;
    font-size: 0.95rem;
    transition: background-color 0.2s;
    margin-top: 1rem;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

.btn-toggle:hover {
    background-color: var(--color-primary-dark);
}

.solution-content {
    display: none;
    /* Hidden by default */
    margin-top: 1.5rem;
    padding-top: 1.5rem;
    border-top: 2px dashed #eee;
    background-color: #fafafa;
    border-radius: 8px;
    padding: 1.5rem;
}

.solution-content.active {
    display: block;
    animation: fadeIn 0.4s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.step {
    margin-bottom: 1rem;
}

.step-title {
    font-weight: bold;
    color: var(--color-primary-dark);
    display: block;
    margin-bottom: 0.25rem;
}

/* Footer */
footer {
    background-color: var(--color-primary-dark);
    color: white;
    text-align: center;
    padding: 3rem 1.5rem;
    margin-top: 4rem;
}

/* Responsiveness */
@media (max-width: 768px) {
    h1 {
        font-size: 2rem;
    }

    h2 {
        font-size: 1.75rem;
    }

    .card {
        padding: 1.5rem;
    }

    .nav-container {
        flex-direction: column;
        gap: 1rem;
    }

    nav ul {
        gap: 1rem;
        flex-wrap: wrap;
        justify-content: center;
    }
}