Have you wondered how a certain aspect or ability in the game works? Here you can present your question, and I will explain to you the answer.

I would like to know how the Hydro Tower works, And all the gfx's and so on. (Sort said I wan't to copy it to my map)
But I am not familiar to Jass is there a way of getting this in odinary triggers?

none whatsoever

How did you create elemental attacks and then elemental armor? Was it a matter of buffs and spells or something else that I'm missing? My hopes were to create a better Ruined Temple TD (Team Survival) using bits and pieces of the Elemental TD map features (like elemental towers). Thanks!

Head under the "Advanced" tab in the World Editor. There you will find " Gameplay Constants" and "Game Interface." You can change the icons and tooltips for the attack and defense types, as well as the damage multipliers.

Warcraft 3 has 8 armor types and 7 attack types hard-coded. Because Element TD uses 6 elements, this worked out perfectly. In the "Gameplay Constants" in word editor, it was a matter of changing the names of the armor types (The actual armor types changed is different than what I'm writing, but you should get the idea)

Armor Types
Unarmored -> Light Armor
Small -> Fire Armor
Normal -> Nature Armor
Heavy -> Earth Armor
Divine -> Water Armor
Hero -> Darkness Armor
Fortified -> Non-elemental Armor
Medium -> Elemental Armor (invulnerable, used only for towers)

Attack Types
Normal -> Composite
Piercing -> Water
Siege -> Fire
Chaos -> Darkness
Hero -> Nature
Magic -> Earth
Spell -> Light

Then new images were made for all armor types, imported using the Import tool in the world editor, and the IMAGES section of "Gameplay Interface" was edited so that these armor and attack types would use the custom images

Finally, under Gameplay Constants, the Damage tables for each attack type were edited so that the appropriate attack type would do 100%, 50% or 200% to the appropriate defense type. The tricky part was that the world editor still calls all armor by the hard-coded names, so I had to keep a cheat sheet so I wouldn't make mistakes.

What do you mean with hard-coded?

Anything "hard-coded" is an irremovable aspect of the game or program. It's like how the game comes with the stats for a peasant. Those stats are hard-coded in so that you can never remove it. For the Element TD we're using a lot of hard coded aspects of Warcraft III, such as the 3d models, creeps, and landscapes.

You can't make more attack types or armor type. You have to work with what Blizzard added.

Well, you can cheat a bit but it's usually prohibitively slow.

Well something I googled and still couldnt do was change a unit into a hero and give it abilities.

Can anyone help me with this?

(e.g I tried turning an Acolyte*the scourge builder* into a hero but it stayed as a normal creep)

You have to think 2 ways.
You cannot turn an acolyte to a hero,
BUT
you can turn a hero into an acolyte.

(lol, could be a story)

just create a new hero, change how it looks and abilitys and so.
Need more help? You can PM me or create a new topic.

What are the rules that determine how the game chooses elements for random mode (i.e. when it is allowed to begin picking lvl3 elementals, when it stops picking interest)?

first lvl2 at 25 (used to be 20 but was changed after discussions in restricted forums/IRC). first lvl3 at 45. interest afaik can be randomed anytime but tends to be more towards mid-game. we had a discussion on this somewhere in dev/beta forums.. that random was too 'difficult' in terms of early higher-tier elementals, too much interest randomed and how to have less randOOmed games..

And there is a cap of 2 x interest, although that cap is broken in the 4.0pb, but will br fixed in the next public version (that is, in the private betas it has been fixed).

I want to mention additionally:
Additional Pures are possible! But you need a Level 3 element. (=> very rare)

So, in summary:
You will get no more than 2 interest picks
You will get a level 2 elemental no earlier than lvl 25
You will get a level 3 elemental no earlier than lvl 45

And that's it? Is that right? Can I get a definitive answer?

you missed out one point which kaini brough up..

you can random extra essence if you have a tier3 elemental already summoned. When the game tries to summon that element, it gives an essence instead. so you can have 3 pures in a rnd game..

Is the probability of getting a certain element pick equal to that of getting an interest pick (i.e., 1/7 chance of getting D [an essence if you already have D3], 1/7 chance of getting L [an essence if you already have L3], ... , 1/7 chance of getting interest), for the entire game?

Yes, unless you already have two interest (the cap).