Just as a bit of background I just finished my A Levels studying Computer Science which was all in Python, so I don't really have much experience with low-level coding or coding in general, but I have dabbled in C# and (very little) C++, and I've made some basic websites from scratch.

I'm not a fan of Python (whitespace as syntax seems insane to me) but from what I can tell without a Googling spree, your project looks really impressive for school. It looks like you understand how to deal with logic which is most of the challenge in learning to program. I have no idea how experinced you are with programming in general. Unless you correct me, I am going to assume that you are experienced enough to be able to code (with Googling as needed) anything you want in high level languages like Python and understand the concept of pointers but haven't worked too much with them.

I am planning on learning ASM using the Sean McLaughlin Z80 in 28 Days website.

That's a good tutorial. But, before you jump into asm, you should make sure that you are very comfortable dealing with pointers and memory. A good way to do so is to make a doubly linked list in Axe. It doesn't need to be efficient but it will force you to work a lot with pointers. The hardest part will probably be allocating memory. A simple way to do that is to allocate a large block of data with GetCalc() and put your list entrys in there, keeping track of free space as you allocate and deallocate list entries. If you can do that, you are ready for asm.

E37 Can I ask how you learned assembly? Just curious how you got to be so proficient at it. I do think dedicating my time to creating some USB Axiom would be a worthwhile thing, especially as it would benefit future developers whatwith the link cable being so iffy, but I obviously need to learn some asm first 

A USB axiom would be less about learning asm and more about figuring out how the USB port works. All you should need is a couple asm snippets that let you read and write to the various ports. Once you have it all figured out (which will almost certainly be very difficult - I counted 31 USB related ports!) there will be time to figure out how to turn it into an Axiom. Here: ':X:Asm(7DD3(123))' writes the lower 8 bits of X to port 123. And ':Asm(DB(123)6F2600)->X' sets X to the 8 bit value read from port 123. In both, the port number can't be a variable. The little documentation that exists for the USB ports is is here. You could also look at USB related BCALLS (and disassemble them) to see how Ti-OS does communication but that would involve learning assembly and trying to figure what Ti was doing when they wrote the OS is not very high on my list of fun activities.

I learned by writing short Asm snippits, converting them to hex and sticking them in my Axe projects. One of the most important tools I had was a little Axe program that took any program and converted its bytes into hex. It is pretty simple to write, just loop over every byte in order, convert it into hex and dump that hex into an output program. I used that program a lot when I was learning asm. Any time I wanted to know how Axe did something, I would make the shortest possible Axe program that did the thing, compile it and then turn that compiled program into hex. I then used this to (manually) decode the hex to actually readable asm. It was very useful for figuring out all the basics. The compiled code that Axe produces is a lot worse than what an experienced asm programmer could make but it also happens to be alot easier to follow the flow of logic since it doesn't do any super advanced tricks. An important thing to remember is that Axe puts all of its built in functions like Pt-On() at the very end of the program (right before data like strings and sprites). Since Axe's built in functions are written in asm and very heavily hand optimized, they are very diffuclt to follow. If you want to see all of Axe's built in functions check out the Developers/Commands.inc file in the Axe Parser download. (shortcut) Some have comments but unless you are looking for something very specific or very general, you probably won't learn much.

When you are debugging, it is super helpful to see register values. If you are programming on the computer, Wabbitemu has some super helpful tools for just that. If not, you can set the value of one of Axe's variables to the value of the register and use Disp to print it out. Just remember that Disp modifies the contents of all the registers so you need to push all the ones you care about before calling Disp and pop them after.

Axe puts the results of its calculations in the HL register. So the line 'X+5' would put the result of X+5 in HL. the line '->X' would store the value currently in HL to X. This is useful as you can do Asm(<some hex>)->X and it would put whatever the final value of HL was in X. The line 'X:Asm(23)->X' Is the same as doing 'X++'. A nice way to verify this is to make an Axe program that is just the line X++ and then disassembling its compiled output. Knowing how to interface with Axe isn't needed when learning but it can make your life a lot easier, especially if you want to skip writing boring calculations in asm or use one of Axe's built in funcitons. Playing around with push hl and pop hl to save variables is a fun starting task and one feature that I think Axe is missing. For example ':X:Asm(E5):SomeFuncitonThatModifiesX():Asm(E1)->X' would let you preserve the value of X. I use that so often in my own Axe code that I made a basic axiom to do just that.

When you are ready to write more complex asm code, Mimas is the best on-calc tool I have found. I did notice that it corrupts the program rarely if you leave it alone for long enough to shut down so make sure to save and quit before leaving your calc. It also comes with handy utilities for converting to and from its internal format and text based asm files you can read and modify on your pc. Of course, there are quite a few PC based tools. I use spasm-ng. (for no other reason than that is what Axe was written in - I didn't do a comprehensive study) Different assemblers may use slightly different syntax for things like macros so if your assembler refuses to compile a some code you found on the internet, that could be why.

Learning asm is not an easy task. Luckily, z80 asm is (in my opinion) one of the easiest ways to learn asm. It has a fairly good suite of instructions without any of the complexities that come with a modern architecture like i386. Schools seem to usually teach RISC based instruction sets which can be easier to learn but are (again, my opinion) much more work to use as they only support a couple very simple instructions. Plus z80 doesn't make you deal with relative addressing that many architectures have. It is important to remember that different architectures have their own quirks and tricks from one may not carry over to another. It was a huge shock going from low level calc programming to low level pc programming. Things like cache and speculative execution take the nice optimization strategy of just counting instruction cycles and throw it out the window and SIMD is there to offer great performance at the cost of learning way more instructions. I have been programming for 8 years and the only constant has always been that me from 6 months ago had no idea what they were doing.

@Xeda112358 is way better at asm than me and might have some suggestions for stuff that I missed.

@ClainBill
The first question is how sure are you that your link cable is good? I wouldn't be surprised if a cable not designed for linking doesn't work. I had a generic cable years ago (and lost it) but was never able to get it to work. A good way to verify this is using the built-in linking tools. Ti-OS has functions like GetCalc( which lets you send variables from one calc to another over a link cable. Or you could use 2nd-X to open the link menu on both calcs and use that to transfer something. If you can send a variable from one calc to another, the cable and link ports are good. If you can't, then there isn't any point in continuing further.

If you are familiar with assembly, you can use Port 0 and try setting a line low on one calc and see if it is pulled low on the other calc. If you aren't, I can write you some simple hex to use it in Axe once you verify the cable can actually transfer data with Ti-OS.

@Ki1o

The game runs at 15MHz but that is mostly because of graphics. Without drawing, the game could easily run at 3MHz. If I wrote everything in assembly, I could probably get it in its current state to run at 6MHz but it relies on other hardware features of the TI-84+ so it will never run on an 83. Compiled, it is over 100k of executable code. Does the 83 even have that much flash? I guess I could compile the game as an OS but that is way too much work.

The font is my text axiom. You can do the same thing with the built in Text command but that requires a font hook which requires some Asm work. Axe normally just calls TI-OS's text drawing command which is why mine is so much faster.

@Ki1o
You are making this way harder than it needs to be. All you need is an if-else chain like this:
If getKey(1)

ElseIf getKey(2)

ElseIf getKey(3)

ElseIf getKey(4)

End

To answer you original question, I don't see anything wrong with your logic. The UpdateState isn't initialized when you code first starts but it isn't initialized in your original code either. Beyond that, I don't know. I don't think I have ever actually used sign{} in serious code so it is possible but very unlikely that there is a bug there. The full source would be useful in troubleshooting because I don't see any problems with what you have. I'm not sure what you are doing with UpdateState in general. Are you are trying to make some kind of state machine? I would avoid that if possible as state machines like that can be way harder to debug than Goto spaghetti. (Source: I do that for a living)
I did notice the line 'PlayerX+sign{I-1+°DirY}→PlayerY' That PlayerX is either a typo or a bug.


A quick code critique:
In both this snippit and the code on GitHub, I noticed that you tend to over complicate logic and rely heavily on indexing into arrays. Both are great ways to spend 80% of your time debugging. Here is how I would write movement code. I have a bit more code than your example but I am doing more checks.

1→°KDown+1→°KLeft+1→°KRight+1→°KUp .add some constants for the arrow keys. In my code I define every key like this. Now, I don't have to remember that 2 is left, I just type °KLeft
15→°KClear

Lbl UpdatePlayer

getKey(°KClear) or Quit→Quit .getKey returns either 1 or 0. I use 'or' so as not to set Quit to 0 if it was 1 when we got here. This should be moved to the main loop since it isn't player related code.

If ScrollXOffset
If >>0
ScrollRight()
ScrollXOffset--
.-4??PlayerX++ .If you want to make PlayerX change on the boundary of tiles instead of when movement starts, you can uncomment this and remove the PlayerX++ from the getKey block below
Else
ScrollLeft()
ScrollXOffset++
.+4??PlayerX--
End
Return .Don't let the player push keys during scrolling
ElseIf ScrollYOffset .Doesn't need to be an else-if (because of the Return in the line above) but it doesn't hurt anything and makes the intent clearer
If >>0
ScrollDown()
ScrollYOffset--
.-4??PlayerY++
Else
ScrollUp()
ScrollXOffset++
.+4??PlayerY--
End
Return
End
.If execution makes it here, both ScrollXOffset and ScrollYOffset are 0. The screen isn't moving so it is safe to pick a new direction

.getKey(num) commands are very quick. Don't be afraid to check the same key multiple times if it makes your code cleaner. It *is* possible that the key state changes between checks but unlikely. As long as you keep that in mind, it is totally fine to do.
If getKey(°KDown) ? getKey(°KUp)-1 .getKey(°KUp)-1 is the same as getKey(°KUp)=0. Checking both keys makes the player not move if up and down are both held. It is a preference thing and not needed if you don't like it
If Walkable(PlayerX, PlayerY+1) .Or whatever check you use to see if the player is allowed to walk into a given tile. I check this inside the if-else chain so that the walkable status of a tile doesn't impact what direction the player is moving.
PlayerY++
8→ScrollYOffset
Goto UpdatePlayer .This is optional. Without it, the player will spend one tick standing still for each tile they move, making movement seem slightly jerky on an actual calc
End
ElseIf getKey(°KUp) ? getKey(°KDown)-1
If Walkable(PlayerX, PlayerY-1) .You don't check for collision in your code. I assume that will be added later? If it doesn't apply, just remove the 'If Walkable' statements
PlayerY--
-8→ScrollYOffset
Goto UpdatePlayer
End
ElseIf getKey(°KRight) ? getKey(°KLeft)-1
If Walkable(PlayerX+1, PlayerY)
PlayerX++
8→ScrollXOffset
Goto UpdatePlayer
End
ElseIf getKey(°KLeft) ? getKey(°KRight)-1
If Walkable(PlayerX-1, PlayerY)
PlayerX--
-8→ScrollXOffset
Goto UpdatePlayer
End
End
.I only did a couple minor optimizations in this example since my goal was readable code. There is quite a bit that can be done with this code but that is left as an exercise to the reader.

Return


@Ki1o Sorry I took so long, I forgot.
I sent your code to my calc and gave it a look. The code in its original state worked fine as a program and an app. As a program, it leaves garbage all over the homescreen on quit. Adding a 'ClrHome' in Exit will fix that. The total compiled program is only 8k bytes total. Since probably 1k of that is data, you still have some space to play with before you hit the execution limit.

When I uncommented all of your AI code, it consistantly corrupted regardless of whether it was a program or app. I also noticed that the slimes always ignored walls - even before corrupted garbage showed up on screen. I am still digging around but my guess is that bu the time the character walks around that big loop, the slimes move so far out of bounds that they corrupt some area of memory. Regardless of what the cause is, as far as I can tell, it has to do with the mob AI and not compiling as an app.

I don't see any overflow protection for A* pathfinding although I could have missed it in the complex logic. Right now you create appvFLOOR before appvDISTMAP. Try creating appvDISTMAP first (Just invert the order of the two GetCalc lines in main) If you are overflowing, that should change the overflow behavior. If you aren't then nothing should change. I noticed you used sign{ in quite a few places. I don't know what that is supposed to be, my best guess is the signed{} command. If it is nib{} then that would be the source of your problems. But, based on how you are using it, it looks like signed{} which is fine. The line 'Fill(^^oTargetX,400,0)' seems a little strange but it should be safe. I don't have any other suggestions, I took a hard look at it for over an hour and didn't see any red flags. Do you reset ram after every time you quit normally?

Also that is some beautifully optimized tile drawing code.

@burro_ciao
Alright, I double checked TI Connect CE's supported calcs and it doesn't support the TI-83. So that's unfortunate. I guess you are stuck using TI Connect. You will need to reset your calc's ram before and after doing pretty much anything when dealing with TI Connect. I haven't actually dealt with connecting an 83 to a PC as I just work with 84s. Try resetting your ram, plugging it back in and if that doesn't work, try a couple more times. Sometimes it just doesn't feel like working. Restarting TI Connect or even you PC might help too.

There are other linking programs out there. TILP is pretty good. You can download it here. You have to pay attention while installing it because it requires GTK2+. It will run the GTK2+ installer after its installer by default. When going through the GTK2+ installer you MUST enable the 'compatibility dlls' checkbox or TILP won't work. I just installed it on my Windows 10 partition and it works fine for me (at least it launches, I haven't tried sending files with it) so if it doesn't work for you, chances are you missed a step while installing. If that doesn't work even after a couple ram resets, you might try looking around on the internet for other linking software. Its possible that your link cable or other hardware is bad.

If you just want to send things to your calc, resetting all memory might fix things. But that will wipe anything in flash.