The teenagers are performing tricks on their bicycles at night.
Kids are playing outside at night.
Kids performing on their bikes may not be "playing outside at night" -- they could be performing in a show.
exists e1 x1 x2 x3 x4.(n_bicycle(x3) & of(x3,x1) & n_thing(x1) & n_teenager(x1) & at(e1,x4) & n_night(x4) & on(e1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_perform(e1) & n_trick(x2))
exists e1 s1 x1 x2.(at(e1,x2) & n_night(x2) & a_outside(s1) & Manner(e1,s1) & Actor(e1,x1) & v_play(e1) & n_kid(x1))