:root {
    --duo-green: #58cc02;
    --duo-green-dark: #58a700;
    --duo-red: #ff4b4b;
    --duo-red-dark: #ea2b2b;
    --duo-blue: #1cb0f6;
    --duo-blue-dark: #1899d6;
    --duo-gray: #e5e5e5;
    --duo-gray-dark: #cecece;
    --duo-text: #3c3c3c;
    --duo-white: #ffffff;
    --radius: 16px;
    --btn-height: 50px;
}

body {
    font-family: 'Nunito', 'Segoe UI', sans-serif;
    background-color: #f7f7f7;
    color: var(--duo-text);
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

header {
    background-color: var(--duo-white);
    border-bottom: 2px solid var(--duo-gray);
    padding: 0 20px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    font-weight: 800;
    font-size: 24px;
    color: var(--duo-green);
    letter-spacing: -1px;
    text-decoration: none;
}

.container {
    max-width: 600px;
    margin: 0 auto;
    padding: 20px;
    flex: 1;
    width: 100%;
    box-sizing: border-box;
}

/* Category Grid */
.category-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 15px;
}

.category-card {
    background: var(--duo-white);
    border: 2px solid var(--duo-gray);
    border-bottom-width: 4px;
    /* 3D effect */
    border-radius: var(--radius);
    padding: 20px;
    cursor: pointer;
    transition: transform 0.1s, border-bottom-width 0.1s, margin-top 0.1s, background-color 0.15s;
    text-decoration: none;
    color: inherit;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.category-card:active {
    transform: translateY(2px);
    border-bottom-width: 2px;
    margin-top: 2px;
}

.category-card:hover {
    background-color: #fcfcfc;
    border-color: var(--duo-gray-dark);
}

.category-info h3 {
    margin: 0 0 5px 0;
    font-size: 18px;
}

.category-info p {
    margin: 0;
    font-size: 14px;
    color: #777;
}

.progress-ring {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    border: 4px solid var(--duo-gray);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 12px;
    color: #aaa;
}

/* Completed state */
.category-card.completed .progress-ring {
    border-color: var(--duo-gold, #ffc800);
    color: var(--duo-gold, #ffc800);
}

/* Quiz Styles */
.question-container {
    text-align: center;
    margin-top: 20px;
}

.question-text {
    font-size: 22px;
    font-weight: bold;
    margin-bottom: 40px;
    color: #4b4b4b;
}

.options-grid {
    display: grid;
    gap: 12px;
}

.option-btn {
    background: var(--duo-white);
    border: 2px solid var(--duo-gray);
    border-bottom-width: 4px;
    border-radius: var(--radius);
    padding: 15px 20px;
    font-size: 18px;
    color: var(--duo-text);
    cursor: pointer;
    text-align: left;
    transition: all 0.1s;
    width: 100%;
    box-sizing: border-box;
    /* Ensure padding doesn't overflow */
}

.option-btn:hover {
    background-color: #f0f0f0;
}

.option-btn:active {
    transform: translateY(2px);
    border-bottom-width: 2px;
    margin-bottom: 2px;
    border-color: var(--duo-gray);
    /* Keep border color consistent */
}

.option-btn.selected {
    border-color: var(--duo-blue);
    background-color: #ddf4ff;
    color: var(--duo-blue-dark);
}

.option-btn.correct {
    border-color: var(--duo-green);
    background-color: #d7ffb8;
    color: var(--duo-green-dark);
}

.option-btn.wrong {
    border-color: var(--duo-red);
    background-color: #ffdfe0;
    color: var(--duo-red-dark);
}

/* Footer Check Bar */
.footer-check {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--duo-white);
    border-top: 2px solid var(--duo-gray);
    padding: 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    /* transform: translateY(0); Always visible */
    transition: background-color 0.2s;
}

.footer-check.correct {
    background-color: #d7ffb8;
    border-color: transparent;
    color: var(--duo-green-dark);
}

.footer-check.wrong {
    background-color: #ffdfe0;
    border-color: transparent;
    color: var(--duo-red-dark);
}

.btn-check {
    background-color: var(--duo-green);
    color: white;
    font-size: 18px;
    font-weight: bold;
    text-transform: uppercase;
    border: none;
    border-bottom: 4px solid var(--duo-green-dark);
    border-radius: var(--radius);
    padding: 0 40px;
    height: 50px;
    cursor: pointer;
    transition: filter 0.2s;
}

.btn-check:active {
    border-bottom-width: 0;
    transform: translateY(4px);
}

.btn-check:disabled {
    background-color: var(--duo-gray);
    border-color: var(--duo-gray-dark);
    color: #afafaf;
    cursor: default;
    transform: none;
    border-bottom-width: 4px;
}

.feedback-msg h2 {
    margin: 0;
    font-size: 24px;
}

.feedback-msg p {
    margin: 5px 0 0;
}