"A Cruel Angel's Thesis" (残酷な天使のテーゼ, "Zankoku na Tenshi no Tēze", "Zankoku na Tenshi no These"in Japan) is the theme song of the popular anime Neon Genesis Evangelion performed by Yoko Takahashi. It is used as the opening to the series, and two instrumental versions of it are played in the finale episode, "Take care of yourself." These are "The Heady Feeling of Freedom" and "Good, or Don't Be", scored for violin, piano, and guitar. "The Heady Feeling of Freedom" is a somber and reflective piece for bowed strings and guitar, while "Good, or Don't Be" is played to a light piano and guitar tone. A similar version can also be heard during the intermission between the two parts of Evangelion: Death and Rebirth.