You can hit the front-most block in a lane while they're pausing on the tiles. When your current colour matches the colour on the front of the block you score. Scoring gains energy (as does finishing a level). If the colour doesn't match, you lose energy. When your energy is down to zero, it's game over. If you finish level 10 you've won.
Also, zapping a lane costs a bit of energy. And when a block reaches the target line, it drains some of your energy.
(How much energy you gain or lose is subject to further balancing...)