The magic square below is the sum
of the patterns that these numbers
make. Use them or enter new ones
and then click 
To understand the structure, move the
mouse over the blue arrows and wait.
Look at the pattern that your selection
produces in the square below
The Bottom Right number
(under the blue down arrow)
above is the first number in
the sequence for the square.
By convention it is "1", but
any number can be used.

If you change the bottom row
above and try using "3,2,1,0" 
instead, do you get the same
result as "2,1,0,1"?
    You can also try experimenting
by writing in your own numbers
in the red squares. To see the
totals, press 
The numbers at the top and
the left are the sums for the
diagonal rows - including the
broken diagonals.