[https://support.steampowered.com/kb_cat.php?id=81 Steam support for Macs]
===Using the shop through Steam===
As a Steam player, you access the shop through Steam to purchase premium or silver. If you are unable to see the Steam overlay, you may need to reset the game to fullscreen (not windowed fullscreen). You may additionally need to lower your resolution. This is a Steam/Mac issue, not a Wurm Online issue.
==Use of the mouse==