The maps that you can play on will have two sides, i have made this quick example of what a map could look like:
(I do know that is image is very poorly made, but i suck at this kind of stuff)
There are two players against each other, one on the left side and the other one on the right side, you can only build towers at your own side.
Both players starts with 25 lives and 550 gold.
Both players also start with 325 income, you will get income every 25 seconds.
There will be rounds, you cannot start a round early no matter what, but the rounds will start being easy and then suddenly turn very hard(to make it so a game cannot last forever).
You will have a menu that you can open and close where you can send monsters at your opponent, the more and stronger the monsters costs the higher income you will get by sender the monster.
After you click to send a monster there will go some time before the monster will be send, the time between the monster gets send is different from each monster, such as there can be some goblins that can be send every 2 second and some other goblins that costs more(and give you more income), but can be send every 0.5 second.
There will be different tiers of troops, such as you start with the tier 1 troops wich could be Goblins, Orges, Wolfes ect. Then after you get enough money you can upgrade to tier 2 troops wich could be the snow trolls, the spiders, the snow wolfes ect, sending tier 2 troops at your opponent would ofcourse cost more, but also give you more income than tier 1 troops.
And then finally tier 3 troops wich could be the demon troops.
TL:DR
The Kingdom Rush Version of Bloons Tower Defense Battles.
I really hope that you like my idea, if you have any questions or thinks that something is bad or missing please tell me instead of just straight up saying "this is bad and this sucks and i am a wolf".