How do you beat level 4 on DuBlox

This is how:

Press the "Up" arrow key 2 times,
then press the "Left" arrow key 3 times,
then press the "Down" arrow key 1 time,
then press the "Left" arrow key 1 time,
then press the "Down" arrow key 1 time,
then press the "Right" arrow key 1 time,
then press the "Up" arrow key 1 time,
then press the "Right" arrow key 1 time,
then press the "Down" arrow key 1 time,
then press the "Left" arrow key 1 time,
then press the "Down" arrow key 3 times,
then press the "Right" arrow key 1 time,
then press the "Down" arrow key 1 time and you're done!

The shorthand version of this answer (18 moves) is
U2 L3 D L D R U
R D L D3 R D