The generator matrix

 1  0  0  0  0  0  1  1  1  X  0  0  1  X  0  1  1  1
 0  1  0  0  0  0  0  0  0  0  1  1  1  X  1  X  X  1
 0  0  1  0  0  0  0  0  X  1  X  1  X  1  0 X+1  X X+1
 0  0  0  1  0  0  X  1 X+1  1  1 X+1  1 X+1  1  0  0 X+1
 0  0  0  0  1  0 X+1  1  0 X+1  1 X+1 X+1  0  X  1 X+1  1
 0  0  0  0  0  1  1  X  1  1  1  1  X  1 X+1  X  0  0

generates a code of length 18 over Z2[X]/(X^2) who´s minimum homogenous weight is 12.

Homogenous weight enumerator: w(x)=1x^0+205x^12+462x^14+859x^16+990x^18+964x^20+442x^22+140x^24+26x^26+7x^28

The gray image is a linear code over GF(2) with n=36, k=12 and d=12.
As d=12 is an upper bound for linear (36,12,2)-codes, this code is optimal over Z2[X]/(X^2) for dimension 12.
This code was found by Heurico 1.16 in 3.53 seconds.