It works great on your phone - full screen if you add it to your homescreen.
Example in C :
answer is -5+14e1
Example in D
Calculate the value of the function and first derivative at x=3
answer is f(3)=12 and f'(3)=15
Example in spacetime M
You see two simultaneous lightning strikes in 10 microseconds, one where you are, one 20 km in the x-direction.
Are these events simultaneous for a spaceship flying at 0.5c in the x-direction? (given : atanh(0.5)=0.5493)
answer is strikes happen at (X4 : 11ms) and (x5 : -26ms) - not the same time.