:root {
    --primary: #2563eb;
    --primary-dark: #1e40af;
    --bg: #f8fafc;
    --card-bg: #ffffff;
    --text: #1e293b;
    --border: #e2e8f0;
    --tag-bg: #f1f5f9;
}

body {
    font-family: 'Roboto', sans-serif;
    background-color: var(--bg);
    color: var(--text);
    margin: 0;
    padding: 0;
}

.app-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
    height: 100vh;
    display: flex;
    flex-direction: column;
}

header {
    margin-bottom: 20px;
    border-bottom: 1px solid var(--border);
    padding-bottom: 15px;
}

header h1 { margin: 0; color: var(--primary); }
header p { margin: 5px 0 0; color: #64748b; }

.main-layout {
    display: grid;
    grid-template-columns: 280px 1fr;
    gap: 30px;
    flex: 1;
    overflow: hidden; /* Para que el scroll sea interno */
}

/* SIDEBAR */
.sidebar {
    background: var(--card-bg);
    padding: 20px;
    border-radius: 12px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
    height: fit-content;
}

.filter-group { margin-bottom: 20px; }
.filter-group label { display: block; font-weight: 500; margin-bottom: 8px; font-size: 0.9rem; }

select {
    width: 100%;
    padding: 10px;
    border: 1px solid var(--border);
    border-radius: 6px;
    background: white;
}

.btn-outline {
    width: 100%;
    padding: 10px;
    border: 1px solid var(--border);
    background: white;
    cursor: pointer;
    border-radius: 6px;
    color: #64748b;
}
.btn-outline:hover { background: #f1f5f9; color: var(--text); }

.stats-box { margin-top: 20px; padding-top: 20px; border-top: 1px solid var(--border); font-size: 0.9rem; }

/* CONTENT AREA */
.content-area {
    display: flex;
    flex-direction: column;
    height: 100%;
    overflow: hidden;
}

.actions-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
    background: white;
    padding: 15px;
    border-radius: 12px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}

.btn-primary {
    background: var(--primary);
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: 6px;
    cursor: pointer;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: background 0.2s;
}

.btn-primary:hover { background: var(--primary-dark); }
.btn-primary:disabled { background: #cbd5e1; cursor: not-allowed; }

/* GRID DE PROBLEMAS */
.problems-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 15px;
    overflow-y: auto;
    padding-bottom: 20px;
    padding-right: 5px; /* Espacio para scrollbar */
}

.problem-card {
    background: white;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 15px;
    display: flex;
    gap: 15px;
    transition: box-shadow 0.2s;
    cursor: pointer;
}

.problem-card:hover {
    box-shadow: 0 4px 6px rgba(0,0,0,0.05);
    border-color: var(--primary);
}

.problem-card.selected {
    background-color: #eff6ff;
    border-color: var(--primary);
}

.checkbox-wrapper input {
    width: 20px;
    height: 20px;
    cursor: pointer;
}

.card-content { flex: 1; }

.problem-text {
    margin: 0 0 10px 0;
    line-height: 1.5;
    color: var(--text);
}

.tags { display: flex; gap: 8px; flex-wrap: wrap; }

.tag {
    font-size: 0.75rem;
    background: var(--tag-bg);
    padding: 4px 8px;
    border-radius: 4px;
    color: #475569;
    font-weight: 500;
}

.tag-nivel { background: #e0e7ff; color: #3730a3; }

/* Responsive */
@media (max-width: 768px) {
    .main-layout { grid-template-columns: 1fr; overflow-y: auto; }
    .sidebar { margin-bottom: 20px; }
    .problems-grid { grid-template-columns: 1fr; }
    .app-container { height: auto; }
}