"Castle of Glass" uses electronic elements from the band's previous studio album, A Thousand Suns.Loudwire noted in their Living Things review that the song features "very different electronic elements and unique sounding samples that the band have added to their musical palette." Yet is one of the most direct that the band has done, with a traditional song structure and a melody reminiscent of country music.
"Castle of Glass" has received mixed to positive reviews from critics. Billboard wrote in their review of Living Things, "A folk song with LP's muscle, "Castle of Glass" uses compelling songwriting, extended metaphors and a simple but radical (for Linkin Park) arrangement to offer one of the album's most intriguing tracks." A staff reviewer at Sputnikmusic wrote in their mixed review of Living Things that the song sounded too similar to "Powerless" and that the song "would have been better if it wasn’t inferior to the similar sounding final track." AltSounds described "Castle of Glass" in their album review as "a drawn-out filler track that keeps to a crawling pace, is strangely passive and doesn’t leave you feeling very inspired." The song was nominated for the "Best Song in a Game" award at the 2012 Spike Video Game Awards.
The music video for Castle of Glass was recorded on August 1, 2012 and it contains footage from the first-person shootervideo gameMedal of Honor: Warfighter. It was released on Linkin Park's YouTube channel, linkinparktv, on October 10, 2012. The music video shows a young boy being told that his father has been killed in action. He and his mother mourn the death as the fallen SEALs teammates and their families try to comfort them. The band is shown playing with a storm where shattered pieces of glass circle the band. Towards the end the boy goes through his father's possessions, fast forwarding to him (played by Marine Corpsveteran Scott Levy) becoming a SEAL, like his father before him. At the end of the video we see the man telling a girl the heartbreaking news of her family member, as she too cries. The video hints at the boy and the woman being the family of Rabbit, who died in the previous game and the teammates being Voodoo and Preacher. True to the Medal of Honor philosophy, Castle of Glass highlights the emotional realities soldiers and their families face far from the battlefield. The video ends with a quote from Winston Churchill, shown in all-caps:
All great things are simple,and many can be expressed in single words:
freedom, justice, honor, duty, mercy, hope.
The band's part of the music video was filmed entirely in front of a green screen, with the production being handled by Mothership and Digital Domain. Its post-production relied heavily on CGI animation and After-effects. Special effects have a prominent use in this music video, and also continues the motif of a world falling apart, as with the previous Living Things videos. One of these is an opening shot of Mike Shinoda, beginning with a shot under, moving progressively upwards until the walls around him start to crumble. The music video also picks up on suspended animation techniques, which sees objects in a fixed position in air, literally suspended, with a central subject being the one animate in this point of fixed time.