ska chords: G   C
E|-3-----|
B|-3---5-|
G|-4---5-|
D|-5---5-|

The ska part is the same throughout, and it is:
  G   G   G   G |  C   C   C   C |
1 + 2 + 3 + 4 + |1 + 2 + 3 + 4 + |

And every power chords section is the following progression, changed
only in speed:

G  G  C  D