The vectors must be fairly short,
the vectors are constrained to:

    ( -10   <   x   <   +10 ) and
    ( -10   <   y   <   +10 )

Create two vectors then press the "A + B" button.

Create vectors by moving the cursor to the origin,
then press and hold the mouse button while dragging
the mouse away from the origin and release the mouse
button when you have the desired vector.

Vectors will "snap" to the nearest grid line ( an integer value ).

Would you like to be less restricted ? Ok.

The first vector can be a little longer:

    ( -15   <   x   <   +15 ) and
    ( -15   <   y   <   +15 )

The second vector will be restricted, bound by a lightly drawn
yellow rectangle, and the constraints may or may not seem
reasonable, but there is a reason, which may become apparent.

The constraints on the second vector depend on the first vector.

Making the first vector relatively long will result in having
the constraints be drawn more tightly on the second vector.

After you create two vectors, you may use any of the buttons labeled:

  "A + B",   "B + A",
  "A - B",   "B - A"

You can press any of these buttons,
and any combination of the buttons.

When multiple vector operations are requested, they will drawn together
( the previous resultant vectors are not erased ).

The graph may move when you first press one of the vector addition
or subtractions keys.

I guarantee that no resultant vector will ever
run off the edge of the grid ( it may go right to the edge ).

Let me know if you can create vector that does go beyond the edge ...

    ( But I know that you can't. )

When a vector subtraction operation takes place the negation of sutracted
vector will be drawn in orange, this vector is added to the other vector
to create the resultant vector.

There is a "hints" line at the bottom of the right panel which flashes
simple, friendly hints and an "out of bounds" warning at approriate times.

I've often wondered if people actually read the instructions ....