Animation of Lines
Draw lines y=x and y=-x. Create a slider say 'c'. Then insert any number of points on previous lines such as (c,c), (-c,c), (c,-c), (-c,-c), (c+1,c+1)..., Now draw perpendicular lines in each point to y=x and y=-x. Change color of lines. Then animate slider 'c'.
Can you notice some plane figures such as squares, rectangles and triangles form as Tessellation.