Love the slider bars. They really show how the graph changes for each parameter. Checked against a few quadratics and it appears to be working fine.
In mathematics, you don't understand things. You just get used to them.
I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.
Woah that is cool!!
I would love you if you created a function grapher, you know, graphing y=x y=e^x .....