/* ======================= Estilos Globales ======================= */
html {
    font-size: 62.5%; /* 1rem = 10px */    
    height: 100%;
}

body {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    margin: 0;
    font-family: Arial, sans-serif;
}

*::before, *::after, * {    
    box-sizing: border-box;
}

:root {
    --font-color: #FEFCFB;
    --bg-color: #034078;
}

h1 {
    font-size: 3rem;    
}

h2 {
    font-size: 2.8rem;    
}

h3 {
    font-size: 2.4rem;    
}

img {
    max-width: 100%;
    object-fit: cover;    
    display: block;
}

/* ======================= Utilidades ======================= */
.container {
    max-width: 100%;
    margin: 0 auto;
    padding: 0 1.5rem;
    flex: 1;
}

.btn {
    font-size: 1.4rem;
    padding: 0.2rem 0.6rem;
    width: 15rem;
    height: 2.5rem;
    border: none;
    border-radius: 0.5rem;
    background-color: #007bff;
    color: white;
    cursor: pointer;
    transition: background-color 0.3s ease, transform 0.2s ease;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);            
}

.btn:hover {
    background-color: #0056b3;
}

.btn:active {
    background-color: #004494;
    transform: scale(0.98);
}

.btn:disabled {
    background-color: #6c757d;
    cursor: not-allowed;
}

/* ======================= Header ======================= */
.header {
    padding: 1rem;
    color: var(--font-color);
    background-color: var(--bg-color);
    width: 100%;    
}

.header h1 {
    text-align: center;    
}

/* ======================= Main ======================= */
.main {
    display: flex;
    flex-direction: row-reverse;
    justify-content: center;
    align-items: center;
    height: 55rem;
    gap: 2rem;
}

@media (max-width: 768px) {
    .main {
        flex-direction: column-reverse;
        margin: 4rem 2rem;
    }

    .chess-board {
        margin: 4rem;
    }

    .options-wrapper {
        width: 35rem;
    }
}

.options-wrapper {
    display: flex;
    flex-direction: column;
    gap: 2rem;
    width: 40rem;
    justify-content: space-between;
    background-color: var(--bg-color);
    color: var(--font-color);
    padding: 2rem;
    border-radius: 1rem;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

label, select, option {
    font-size: 1.4rem;
}

select, option {
    padding: 0.2rem;
}

fieldset {
    border: 1px solid #ccc;
    border-radius: 0.5rem;
    padding: 1rem;
    margin-bottom: 1rem;
}

legend {
    font-size: 1.6rem;
    font-weight: bold;
    padding: 0 0.5rem;
}

.label-option {
    margin-right: 0.5rem;
}

.button-group {
    display: flex;
    justify-content: space-around;
    align-items: center;
}

.color-options {
    display: flex;
    justify-content: space-around;
    align-items: center;    
}

.chess-board {
    border: 2px solid #333;
    border-collapse: collapse;
    margin: 0rem 10rem;
    width: 40rem;
    height: 40rem;
}

.chess-board td {
    width: 4rem;
    height: 4rem;    
    position: relative;
    padding: 0.5rem;
}

.chess-board td img {
    width: 100%;
    height: 100%;
    object-fit: contain;
    display: block;
    position: absolute;
    top: 0;
    left: 0;
    padding: 0.3rem;
}

/* Default color scheme */
.chess-board tr:nth-child(odd) td:nth-child(even),
.chess-board tr:nth-child(even) td:nth-child(odd) {
    background-color: #d49f67;
}

.chess-board tr:nth-child(odd) td:nth-child(odd),
.chess-board tr:nth-child(even) td:nth-child(even) {
    background-color: #52311e;
}

/* White and Black color scheme */
.chess-board.white-black tr:nth-child(odd) td:nth-child(even),
.chess-board.white-black tr:nth-child(even) td:nth-child(odd) {
    background-color: white;
}

.chess-board.white-black tr:nth-child(odd) td:nth-child(odd),
.chess-board.white-black tr:nth-child(even) td:nth-child(even) {
    background-color: black;
}

/* Blue and Yellow color scheme */
.chess-board.blue-yellow tr:nth-child(odd) td:nth-child(even),
.chess-board.blue-yellow tr:nth-child(even) td:nth-child(odd) {
    background-color: blue;
}

.chess-board.blue-yellow tr:nth-child(odd) td:nth-child(odd),
.chess-board.blue-yellow tr:nth-child(even) td:nth-child(even) {
    background-color: yellow;
}

/* Red and Green color scheme */
.chess-board.red-green tr:nth-child(odd) td:nth-child(even),
.chess-board.red-green tr:nth-child(even) td:nth-child(odd) {
    background-color: red;
}

.chess-board.red-green tr:nth-child(odd) td:nth-child(odd),
.chess-board.red-green tr:nth-child(even) td:nth-child(even) {
    background-color: green;
}

/* ======================= Footer ======================= */
.footer {
    background-color: var(--bg-color);
    color: var(--font-color);
    padding: 2.4rem;
    text-align: center;
    font-size: 1.6rem;
    margin-top: auto;
}

@media (max-width: 768px) {
    .footer {        
        font-size: 1.4rem;
    }
}

.footer p {
    margin: 0;
}