So when I grow up I want to be a programmer so I decided to make a tower defense on my ti-84 plus so anyway I need help to figure out how to start it thanks.

Well first off, we need to know a little bit more information. Is this going to be made using Ti-Basic, Axe, or Asm? And a tower defense is a bit of work.. So if you are comfortable with making one, by all means go for it!

Tower defense games are not really that hard. I made one but never released it for the PC. What I did was have different tiles and each tile also had associated data which stored direction start finish and vertical and horizontal flip the background tiles. The enemies followed this path based on direction at that tile. As they move range checks are done on the enemies to see if they can be shot at. If so the tower will move at most of n angle (this is a limit I created to add more difference between towers and can be upgraded of course by using points/cash) if it cannot move fast enough it will try and follow the enemy. It will then subtract p from l where p = power of the ammunition and l = life points of the enemy. Optionally depending on life points the graphics of the enemy can be altered. For example in balloons tower defense the balloon changes color. As expected when l<=0 the enemy is destroyed.

Sorry about that it would be Ti-Basic and I am comfortable with making a tower defense game

I don't see how programming language matters at this point. From the question it appears he just wanted a description on how to make a tower defense which I addressed in my previous post. Did it help you?

What kind of projects have you worked on in the past? Take a look over the description of how a Tower Defense game works in general that ProgrammerNerd posted, and tell us if that makes sense to you. If not, I recommend you start with a few smaller projects work. You might find "Chapter 5: Theory interlude: problem solving and debugging" from "Programming the TI-83 Plus/TI-84 Plus" particularly helpful if you don't have much experience turning an idea into a completed program. We are here to help if you have any follow-up questions.