We all hate those circular marks left behind as evidence of us having left our cold beverage glasses on furniture surfaces. Here’s a great way to protect your furniture from these, with warning signs from the Portal game adding to the aestheticism of it all. These coasters each sport one of those warning signs you’d come across while playing Portal 2 and come in a pack of eight, each with a different sign. Measuring 3.5″ x 3.5″ each, these are officially licensed Portal collectibles and come with an equally awesome black storage container for them to stack up when not playing superhero for your furniture. Portal 2 warning signs coasters are available at ThinkGeek for $20.