Touch and slide the balloons and weights on the left-hand edge to place them in any empty square.
Balloons will rise until they hit an obstacle, while weights will fall until they hit an obstacle.
Balloons and weights that have already been placed will act as obstacles themselves.
If there are multiple weights or multiple balloons in an area, it will turn red to indicate that this isn't allowed.
But when there is exactly one balloon and one weight in an area, it will turn blue.
Blue will do!
Answer for 'Rise to the Challenge 18'
The answer is as follows.