Instructions
Form the Lines Here
Keep your stacks low. As the blocks reach the top of the screen, the situation can get hairy for you quickly at the later levels. Place the blocks horizontally and to the sides whenever you can to keep the stack low.
Pack the blocks (or tetrads) tightly to prevent gaps, and place a block that fits a gap perfectly whenever you can to keep the lines even.
Practice making tetrises. These occur when you use the long block to make four lines at one time. It's easy to do at the early levels, but much harder when the blocks start to descend more quickly. As you get better at maneuvering the blocks, you can try for more terises at the later levels.
Keep an eye on the next tetrad. A window in the lower-right section of the screen shows the next block that will drop, and can help you decide where to place the current block.
Practice different tetrad placements. Some moves look odd at first, but are effective nonetheless. For example, you can sometimes form a line above a gap with a block. Initially, it appears as if you are creating a gap in your stack that is impossible to access, but the line that is formed actually makes the gap easier to get to.
Do not stack tetrads on top of gaps. Try to complete lines that include the gap-covering blocks to access the gap.
Slide tetrads into gaps. Occasionally, you will be able to access gaps by allowing a tetrad to land and then sliding it into place before it stops moving. The slower the speed, the more you can slide the block.