function sol_group_info_shortcode($atts) {
    $atts = shortcode_atts([
        'user_id'    => get_current_user_id(),
        'group_key'  => 'bronze',
        'group_size' => 10,
    ], $atts);

    $tiers = sol_get_group_tiers();
    $group = $tiers[$atts['group_key']];
    $payout_before_fees = $group['amount'] * ($atts['group_size'] - 1);
    $fee = $payout_before_fees * $group['fee'];
    $estimated = $payout_before_fees - $fee;

    return "
        <div class='sol-group-info'>
            <h3>Tier: {$atts['group_key']}</h3>
            <p>Contribution: \${$group['amount']}</p>
            <p>Fee per payout: {$group['fee']*100}%</p>
            <p>Group Size: {$atts['group_size']}</p>
            <p><strong>Estimated Payout: \$" . number_format($estimated, 2) . "</strong></p>
        </div>
    ";
}
add_shortcode('sol_group_info', 'sol_group_info_shortcode');