[NTG-context] Question about matrices with vertical and horizontal lines

Hi, I’d like to typeset a matrix with vertical and horizontal lines like so: starttext \startformula \startmatrix \HL \VL 16 \VL 3 \VL 2 \VL 12 \VL\NR \HL \VL 5 \VL 10 \VL 11 \VL 8 \VL\NR \HL \VL 9 \VL 6 \VL 7 \VL 12 \VL\NR \HL \VL 4 \VL 15 \VL 14 \VL 1 \VL\NR \HL \stopmatrix \stopformula \starttable[|c|c|c|c|] \HL \VL $16$ \VL $3$ \VL $2$ \VL $12$ \VL \FR \HL \VL $5$ \VL $10$ \VL $11$ \VL $8$\VL \SR \HL \VL $9$ \VL $6$ \VL $7$\VL $12$ \VL\SR \HL \VL $4$ \VL $15$ \VL $14$ \VL $1$ \VL\SR \HL \stoptable \stoptext In the matrix version, the horizontal lines extend too far to the left. Ideally, I would like the cells to be squares, with the entries centered. Thanks for any suggestions! Matthias