Bashing the Bohrok
To do damage to a Bohrok or a Bohrok-Kal, you must get it to unroll. When you're 
battling a Bohrok or Bohrok-Kal as Toa Tahu (the red one)or Gali Nuva (the blue 
one), they will randomly unroll to attack you. 
If you're playing as Toa Kopaka (the silver one), then you must get close enough 
that the Bohrok is targeted. Then, use your shield This will unroll the Bohrok 
(attack it quickly and as many times as possible during the 3 seconds that you 
have before it rolls up again).

Bionacle of light takua nuva
Complete the game with all 6 toa including toa tahu nuva's quest to unlock the 
bionicle of light takua nuva

Extra bonuses:
Complete a level with all Lightstones collected as each Toa to unlock a bonus at 
the Extras menu. 

Destroying dark cages:
Use Nuva Blasts to destroy dark cages. Charge your elemental energy, then 
immediately press Triangle.