-----> Drag the three vertices A, B and C around -----> To single-step a vertex, click it or type it's letter(A,B or C),then use the arrows keys to move that point. Which point is moving can be seen at bottom of screen. -----> Press space to change the color inside the circle -----> See the type of triangle (Acute - Right - Obtuse) or (Isosceles - Equilateral, Scalene) -----> See the values of angles A, B and C and the values of the sides AB, AC and BC.
Added option to move any point by typing it's letter then using arrow keys. Thanks to dapontesgr for original idea and good work!