Don't waste bombs on enemies if you can save them to find Secret Rooms or blow up tinted rocks (rocks with a small 'x' and a blue tint).
School and office networks often use firewalls to block gaming sites like Steam or official developer pages. "Unblocked Games 66 EZ" is a popular mirrored site that hosts Flash and HTML5 versions of classic games. Benefits of playing on 66 EZ: No downloads or installations required. the binding of isaac unblocked games 66 ez
Never enter passwords or personal data on these mirror sites. Don't waste bombs on enemies if you can