Square side pinpointing Welcome to my first code-golf challenge! :) Let's hop right into it.

Challenge:

Given two floating point vectors, O (origin) and T (target), you have to create a program to print the values L and R to STDOUT.


O is one corner of the square
T is one corner of the square that is located opposite to O
L is the 2D point (corner) that marks the other point of the uncomplete square
R is the 2D point (corner) that is opposite to L


Rules


Values for O and T have to be read from STDIN (see example inputs).
Again, L and R's values has to be printed to STDOUT.


Scoring and bonuses


Count the bytes of your program.
If your program draws lines that connect between O to L to T to R, subtract 15 bytes from the byte count.


Examples

First line covers inputs (first square brackets for O and next brackets for T) and other line represents expected output.


[0, 0] [3, 3]
Expected: [0, 3] [3, 0]
[0, 0] [-2, -2]
Expected: [-2, 0] [0, -2]
[1, -1] [4, 2]
Expected: [1, 2] [4, -1]
[0, -1] [0, 1]
Expected: [-1, 0] [1, 0]


NOTICE: inputs and outputs can be floating points!

Important information!


Values O and T can be taken in any format, as long as they come from STDIN (ex. Inside [] or ()...), use whatever format you want.
L and R can be printed in any order.
Remember: when (O->L->T->R->O) are connected, each side must have the same length!


Winning


This is code-golf so fewest byte answer wins!
Winner answer will be accepted at sunday 15.11.2015  20:00-22:00 (Finland time) (If I'm not wrong, that date is written like 11.15.2015 in the US, don't get confused).


Happy golfing!
Seriously, 11 bytes
A port of my TI-BASIC answer. Calculates mean(X)+i*(X-mean(X)).
,;Σ½;)±+ï*+

Explanation:
,           Read input
;           Duplicate
Σ½          Half the sum (the mean) of the top copy
;           Copy the mean
)           Rotate stack to the left
            Now there's a copy of the mean on the bottom
±+          Negate mean and add to input list
ï*          Multiply by i
+           Add to mean

Input as a list of two complex numbers: [1-1j,4+2j], and output in the same format: [(4-1j), (1+2j)].