Love – Fez

This is “Love” from the 2D/3D puzzle game “Fez” by Polytron.
The first half of the song is bright in a major key with a gentle rhythm.
The secondary dominant in the second bar, going to II, gives a sense of sadness in the midst of calmness, and the fact that it starts from sus4 also strengthens the sense of relief when it resolves to II.
The second half seems to drift without landing anywhere, but perhaps it ends with Dm6 (Fmaj7 before that is bIII in D minor key)? I think so.