def setup
  background(220)

  v0 = createVector(1, 2, 3)
  v1 = createVector(2, 3, 4)
  result = P5Vector.mult(v0, v1)

  div = createDiv("result: [#{result.x}, #{result.y}, #{result.z}]")
  div.position(10, 10)
  div.style('font-size', '14px')
  div.style('width', '100px')
end

def setup
  background(220)

  v1 = createVector(1, 2, 3)
  v2 = P5Vector.mult(v1, 2)

  div = createDiv("v2: [#{v2.x}, #{v2.y}, #{v2.z}]")
  div.position(10, 10)
  div.style('font-size', '14px')
  div.style('width', '100px')
end

def draw
  background(240)

  v0 = createVector(50, 50)
  v1 = createVector(25, -25)
  drawArrow(v0, v1, 'red')

  num = map(mouseX, 0, width, -2, 2, true)
  v2 = P5Vector.mult(v1, num)
  drawArrow(v0, v2, 'blue')

  noStroke
  text(format("multiplied by %.2f", num), 0, 90)
end

# draw an arrow for a vector at a given base position
def drawArrow(base, vec, myColor)
  push do
    stroke(myColor)
    strokeWeight(3)
    fill(myColor)
    translate(base.x, base.y)
    line(0, 0, vec.x, vec.y)
    rotate(vec.heading)
    arrowSize = 7
    translate(vec.mag() - arrowSize, 0)
    triangle(0, arrowSize / 2, 0, -arrowSize / 2, arrowSize, 0)
  end
end