Function main is a special function; it runs automatically at game start, so any commands that inside it will be executed when we press the Test Run button . As you can see, the first command level_load loads a level named "small.hmp" (our landscape) and the second command ent_create loads an entity named "earth.mdl" at a position of X = 10, Y = 20, Z = 30 in the level, telling it to simply stay there, without doing anything (NULL). What should we do if we'd like to create another earth.mdl entity on top of the previous one? We should add another command to function main, of course!
function main( )
{
level_load("small.hmp");
ent_create("earth.mdl", vector(10, 20, 30), NULL);
ent_create("earth.mdl", vector(10, 20, 55), NULL);
}
Type the new line of code using SED just like you would use your favorite word processor, and then let's Test Run the project again:
It has worked indeed! The second sphere was created at x = 10, y = 20, z = 55, being placed 25 units (quants) above the first one, which has its z set to 30. The vector keyword simply groups together the x, y, z values under the same umbrella; we will talk about all these concepts later, so don't feel guilty

if you don't grasp them all at once.
SED gives us quick access to the documentation whenever we need it; click the Command Help tab at the bottom of the screen (if it isn't selected already), and then click any engine keyword - you will see its description, just like in the picture below. This comes in handy if you want to write a command, but you don't remember its parameters.