I've played this a couple of times and it sounds right

intro

--------------------------|
------------0-3-0---0-----|
-0---0------------2-------|    Repeat Several Times
---0---0-2-------------2--|
--------------------------|
--------------------------|


Riff 1

G           G
-3----------3------|
-3----------3------|
-0--2-4-2-0-0------|     4 Times
-0----------0------|
-2----------2------|
-3----------3------|


Riff 2

D           Em
-2----------0-----------|
-3----------0-----------|
-2----------0-----------|   3 Times
-0---0------2-----------|
---2---2-0--2-----------|
------------0-2-3-5-----|

Riff 3

--------------------------------------|
--------------------------------------|
--------------------------------------|    4 times, but on the 4th time
--------------------------------------|    do this:
--2-3-2-3-2-3-2-----2-3-2-3-2-3-2-----|
----------------3-----------------3---|

                                           D -----------------2-2-2-2-0--------|
                                           A --2-3-2-3-----------------2-0-----|
                                           E ----------------------------------|

                                                   End on G