/* --- VARIABLES Y ESTILOS GENERALES --- */
:root {
    --color-background: #f8fafc;
    --color-text: #1e293b;
    --color-primary: #193E58;
    --color-primary-hover: #112a3f;
    --color-accent: #f97316;
    --color-accent-hover: #ea580c;
    --color-fixed-text: #1e293b;
    --color-user-text: #2563eb;
    --color-border: #cbd5e1;
    --color-border-thick: #94a3b8;
    --cell-selected-bg: #fde68a;
    --cell-peer-bg: #e2e8f0;
    --cell-same-number-bg: #dbeafe;
    --cell-error-bg: #fecaca;
    --gradient-start: #8a3b0f;
    --gradient-end: #f97316;
}

.dark {
    --color-background: #0f172a;
    --color-text: #e2e8f0;
    --color-primary: #334155;
    --color-primary-hover: #475569;
    --color-fixed-text: #f1f5f9;
    --color-user-text: #60a5fa;
    --color-border: #475569;
    --color-border-thick: #64748b;
    --cell-selected-bg: #4a4a2a;
    --cell-peer-bg: #1e293b;
    --cell-same-number-bg: #1e3a8a;
    --cell-error-bg: #7f1d1d;
}

#sudoku-root {
    font-family: 'Inter', sans-serif;
    background-color: var(--color-background);
    color: var(--color-text);
}

/* --- CONTENEDOR PRINCIPAL --- */
.game-container {
    max-width: 500px;
    margin: 0 auto;
    padding: 16px;
}
.game-main-header {
    text-align: center;
    margin-bottom: 16px;
}
.game-title {
    font-size: 2.25rem;
    font-weight: 800;
    font-family: 'Poppins', sans-serif;
    background: linear-gradient(to right, var(--gradient-start), var(--gradient-end));
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
}
.game-wrapper {
    background-color: #fff;
    border-radius: 12px;
    padding: 16px;
    box-shadow: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -2px rgba(0,0,0,0.1);
}
.dark .game-wrapper {
    background-color: #1e293b;
}

/* --- ENCABEZADO DEL JUEGO (DENTRO DEL WRAPPER) --- */
.game-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 16px;
}
.back-button {
    background: none;
    border: none;
    color: var(--color-accent);
    font-weight: 600;
    cursor: pointer;
}
.difficulty-title {
    font-size: 1.25rem;
    font-weight: 700;
    text-transform: capitalize;
}

/* --- ESTADÍSTICAS DEL JUEGO --- */
.game-stats {
    display: flex;
    justify-content: space-around;
    align-items: center;
    margin-bottom: 16px;
    padding: 8px;
    background-color: #f8fafc;
    border-radius: 8px;
}
.dark .game-stats {
    background-color: #0f172a;
}
.stat-item {
    display: flex;
    align-items: center;
    gap: 8px;
    font-weight: 600;
}
.error-count {
    color: #ef4444;
}
.dark .error-count {
    color: #f87171;
}

/* --- VIDAS (CORAZONES) PARA RETO DIARIO --- */
.lives-container {
    display: flex;
    align-items: center;
    gap: 4px;
    color: #ef4444; /* red-500 */
}
.dark .lives-container {
    color: #f87171; /* red-400 */
}
.extra-lives {
    font-size: 0.875rem;
    font-weight: 700;
    margin-left: 4px;
    color: #f97316; /* brand-orange */
}


/* --- TABLERO --- */
.board {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    gap: 2px;
    background-color: var(--color-border-thick);
    border: 2px solid var(--color-border-thick);
    aspect-ratio: 1 / 1;
}
.cell {
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: clamp(1rem, 4vw, 1.75rem);
    font-weight: 600;
    background-color: #fff;
    cursor: pointer;
    transition: background-color 0.2s;
}
.dark .cell {
    background-color: #1e293b;
}
.cell:nth-child(3n) { border-right: 2px solid var(--color-border-thick); }
.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) {
    border-bottom: 2px solid var(--color-border-thick);
}
.cell:nth-child(9n) { border-right: none; }
.cell:nth-child(n+73) { border-bottom: none; }

.cell-fixed {
    color: var(--color-fixed-text);
    cursor: default;
}
.cell-selected {
    background-color: var(--cell-selected-bg) !important;
}
.cell-peer {
    background-color: var(--cell-peer-bg);
}
.cell-same-number {
    background-color: var(--cell-same-number-bg) !important;
}
.cell-error {
    background-color: var(--cell-error-bg) !important;
    color: #b91c1c;
}
.dark .cell-error {
    color: #fecaca;
}
@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-5px); }
    75% { transform: translateX(5px); }
}
.animate-shake {
    animation: shake 0.3s ease-in-out;
}

/* Notas */
.cell-notes-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    width: 100%;
    height: 100%;
}
.cell-note {
    font-size: clamp(0.5rem, 1.5vw, 0.75rem);
    display: flex;
    justify-content: center;
    align-items: center;
    color: #64748b;
}
.dark .cell-note {
    color: #94a3b8;
}

/* --- BOTONES DE ACCIÓN Y NÚMEROS --- */
.action-buttons {
    display: flex;
    justify-content: space-around;
    margin-top: 16px;
}
.action-button {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 16px;
    border-radius: 8px;
    background-color: #f1f5f9;
    border: 1px solid var(--color-border);
    font-weight: 600;
    cursor: pointer;
}
.dark .action-button {
    background-color: #334155;
    border-color: #475569;
}
.action-button.active {
    background-color: var(--color-accent);
    color: #fff;
    border-color: var(--color-accent);
}

.number-pad {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 8px;
    margin-top: 16px;
}
.number-button, .erase-button {
    padding: 12px;
    font-size: 1.5rem;
    font-weight: bold;
    border-radius: 8px;
    border: none;
    background-color: var(--color-primary);
    color: #fff;
    cursor: pointer;
    transition: background-color 0.2s;
}
.number-button:hover, .erase-button:hover {
    background-color: var(--color-primary-hover);
}
.number-button:disabled {
    opacity: 0.3;
    cursor: not-allowed;
}
.dark .number-button, .dark .erase-button {
    background-color: #334155;
}
.dark .number-button:hover, .dark .erase-button:hover {
    background-color: #475569;
}
.erase-button {
    grid-column: span 1;
    display: flex;
    align-items: center;
    justify-content: center;
}

/* --- PANTALLA DE RESUELTO --- */
.solved-screen {
    text-align: center;
    padding: 24px;
    background-color: #fff;
    border-radius: 12px;
    box-shadow: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -4px rgba(0,0,0,0.1);
}
.dark .solved-screen {
    background-color: #1e293b;
}
.solved-screen h2 {
    font-size: 2.25rem;
    font-weight: bold;
    color: var(--color-accent);
}
.solved-stats {
    margin: 24px 0;
    display: flex;
    flex-direction: column;
    gap: 8px;
}
.solved-buttons {
    display: flex;
    flex-direction: column;
    gap: 12px;
}
.solved-buttons button {
    width: 100%;
    padding: 12px 24px;
    font-weight: 600;
    border-radius: 8px;
    border: none;
    cursor: pointer;
    transition: background-color 0.2s;
}
.solved-buttons button:first-child {
    background-color: var(--color-accent);
    color: #fff;
}
.solved-buttons button:first-child:hover {
    background-color: var(--color-accent-hover);
}
.solved-buttons button:last-child {
    background-color: #e2e8f0;
    color: #1e293b;
}
.dark .solved-buttons button:last-child {
    background-color: #475569;
    color: #e2e8f0;
}

/* --- PANTALLA DE MENÚ --- */
.menu-screen {
    text-align: center;
    padding: 24px;
}
.menu-screen .subtitle {
    font-size: 1.125rem;
    margin-bottom: 24px;
}
.difficulty-buttons {
    display: flex;
    flex-direction: column;
    gap: 16px;
}
.difficulty-button {
    padding: 16px;
    font-size: 1.25rem;
    font-weight: 700;
    border: 2px solid var(--color-border);
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
}
.difficulty-button:hover {
    transform: scale(1.05);
}
.difficulty-easy { color: #22c55e; border-color: #22c55e; }
.difficulty-medium { color: #3b82f6; border-color: #3b82f6; }
.difficulty-hard { color: #ef4444; border-color: #ef4444; }