I'm making an image grid.

```
<div class="row text-center" style="display: flex; flex-wrap: wrap;">
        <% campgrounds.forEach(function(campground) { %>
            <div class="col-md-3 col-sm-6">
                <div class="thumbnail">
                    <img src="<%= campground.image%>">
                    <div class="caption">
                        <h4><%= campground.name %></h4> 
                    </div>
                </div>

            </div>          
        <% }); %> 
    </div>

```

The output I get is [click](https://i.imgur.com/ZlNB77L.jpeg). There is no spacing between images. How to add it? I'm not using any CSS at the moment.