A solution to this problem would be to create a variable (which you’ve already done), but then you need to use some sort of add/subtracting operator (depending if you want it to go down or up).
Then you would put the variable inside the “y” parameter of the text.
Make sure to put it in a draw function too.
Example:
var textStart = 300
function draw () {
textStart -= 1 //you change this number if you want to make it go faster or slower
text("tu planeta", 200, textStart);
}