Thanks ourmanflint.
I”ve added the following for tablets and mobiles so that the content expanded to their widths.
@media screen and (max-width: 783px) {
.site-content .entry-header,
.site-content .entry-content,
.site-content .entry-summary,
.site-content .entry-meta,
.page-content,
.post-navigation,
.image-navigation,
.comments-area {
max-width: 100%;
}
}