this should work, in your tank_move function make a new (or 2 new if's) for rotating:

if(key_cur)
{
vec_set(motor1,vector(-1000,500,0));
vec_set(motor2,vector(1000,500,0));
}
if(key_cul)
{
vec_set(motor1,vector(1000,500,0));
vec_set(motor2,vector(-1000,500,0));
}

hope it works for you.
regards,

Formerly known as dennis_fantasy
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