// Update the position of any blocks that need their position updated
  void update() {
    // Logic for dropping blocks ------------------------
    // Amount of blocks that are falling
    int falling=0;
    boolean clearingLine=false;

    // Iterate through the blocks in the field
    for (int i=blocks.size()-1; i>=0; i--) {
      // Whether to stop the block
      boolean stop = false;

      // If the block is falling
      if (blocks.get(i).fall) {

        // Add 1 to our falling counter
        falling++;

        // Check if the block is below the end of the screen
        if (blocks.get(i).by>=sizey) stop=true;

        // Check if the block has a block below it
        // Iterate through all blocks
        for (int j=blocks.size()-1; j>=0; j--) {
          // If the y value of j is below i
          if (blocks.get(j).by==blocks.get(i).by+1) {
            // If the x values are the same
            if (blocks.get(j).bx==blocks.get(i).bx) {
              // If j is not falling
              if (!blocks.get(j).fall) {
                // Stop i from falling
                stop=true;
                break;
              }
            }
          }
        }

        // Stop falling if stop is true
        if (stop) blocks.get(i).fall = false;

        // Push the block's position down
        if (!stop) blocks.get(i).by++;

        // If the block should move horizontally, move it
        if (moveDir!=0 && !stop) blocks.get(i).bx+=moveDir;
      }
    }
    moveDir = 0;

    // Logic for clearing lines --------------------
    // If no blocks are falling
    if (falling>0) {
      clearingLine=true;
      // Iterate through each line
      for (int i=0; i<sizey; i++) {
        // How many blocks are on this line
        int howMany=0;

        // Iterate through the blocks on the field
        for (int j=blocks.size()-1; j>=0; j--) {
          // If the block is at this line, count it
          if (blocks.get(j).by==i) howMany++;
        }
        // If there are more blocks on this line than the width of the field, clear this line
        if (howMany>=sizex) removeLine(i);
      }
    }
    // If no blocks are falling and we aren't clearing a line, add a new shape
    if (!clearingLine) initializeShape(calculateNextShape());
  }

  // Remove a line of blocks from the field and update the blocks above to fall.
  void removeLine(float line) {
    // Iterate through all lines before the one to be removed
    for (int i=0; i<line-1; i++) {
      // Iterate through the blocks on the field
      for (int j=blocks.size()-1; j>=0; j--) {
        // If the block is at the current line, make it fall.
        if (blocks.get(j).by==i) blocks.get(j).fall=true;
      }
    }

    // Iterate through the blocks on the field
    for (int i=blocks.size()-1; i>=0; i--) {
      if (blocks.get(i).by==line) blocks.remove(i);
    }
  }