I don't know if game will lag for you - it is quite demanding
Maybe try other browser if it will lag?
Complete horizontal lines of blocks in order to get them cleared in exchange for score
The more blocks you clear at the same time - the more score you'll get
Watch out for game over line and try not to be too greedy even if combos are a way for longer game and higher score
It will be tricky to play but you'll get there eventually!
Don't forget to share your best score ^^
There is a small easter egg once
you beat my personal best score =P