When in add new points mode tapping on the screen will add a point. Tapping a second time will add a 2nd point that is joined to the first point by a red line. Further tapping will add more points/lines.
Keeping your finger on the screen and moving it before lifting it up will allow you to drag the endpoint on the new line.
The grey dots are shortcuts that help you line up points. Double tapping on a shortcut will draw a line from the last line drawn to the shortcut.
Single Tapping on a shortcut will draw a dotted red line indicating which dot the shortcut is lining up with.
To adjust an existing line, tap on the line and the ruler will be displayed. You may either tap on an end point of the line and move it by dragging your finger across the screen, or you may adjust the length of the line by moving the ruler.
When moving your finger or moving the ruler, before you lift up your finger the new line is shown and a ghosted version of the original line can be seen.
After lifting your finger the ghosted image disappears and the changed line is shown.
Splitting a line
To split an existing line you need to follow the steps below.
Change mode to Add Points.
Tap on the point where you wish the line to split.
Tap on select mode.
This will automatically split the line at the point where the new point was placed.
Adjust the length of the split line by using the ruler.
To change an existing line to a curved line follow the steps below. Make sure that the building is selected (ie the Building is highlighted in gray).
Select Add/Edit the curve tool. Tap on a point close to the centre of the line and drag the newly added control point to get the curvature of the line correct.
Note that the area of the room associated with the line takes into account the curve.