Help with esp8266 AP serving webpages to clients (CSS not working)

I’ve got my ESP setup to be an AP that serves a webpage and it almost works. (.ino code file attached for reference, NB that it’s messy AF due to debugging, all kinda unused code in it. Open in a syntax-highlighting text editor (NPP is my pref) or the actual IDE and it’ll make a LOT more sense) Also NB that atm my code is using SPIFFS to send a “index.html” file from SPIFFS on-device storage as a sorta “Hello World” test, but it’s the const char HTMLString webpage that I care about. I created it using Tryit Editor v3.6 and both there (there’s a “Try It” thing setup on that website, shows code output in real time) and saved on my HDD as “Index.html” it works as intended, buncha giant, easily-read buttons.

My issue is that NONE of my “CSS/styling” is working when I serve ANY page to a client over the ESP, buttons show up with proper names but they’re totally generic (think WinXP/“radio button”-style); PLUS I can’t get my “". HTML code that’s being send right now is attached as “dashboard_HTML.txt,” it’s CSS file is also attached as “dashboard_CSS.txt.”
HTML stored under variable const char HTMLString is what I WANT to be using, but again, it’s just not working correctly. Here’s a perfect example, In “dashboard.html” objects are setup to be

, but what’s being displayed is just Text; "

22%

Humidity
" produces "22%" and under that is "Humidity" (as seen in "Image_001.jpg".)

This behavior occurs on ANY device I try it on, I’ve tried both Wemos d1 Mini esp8266 clones I bought on Amazon, they has the esp-12f chips in 'em. ArduinoIDE Board manager is set to “Wemos D1 Mini” selection, using default settings ('cept when I has to wipe SPIFFS, then I set it to “Erase Flash: All chip contents” when uploading and toggle it back to “Sketch Only” right away.

I have MANY ideas on what’s happening but I don’t wanna muddy the waters too much. It SEEMS, to me, that for whatever reason CSS isn’t working, so that’s what I’ve used as a title, but we (arduino “Makers”) all know the culprit could just be a lousy gd typo or the IDE having a hissy fit over it’s own stupidity or some other stupid shit.
So that’s my story, hope you enjoyed reading it, also hope someone can help.
ty in advance for any help offered, I’m at my wit’s end, been stuck right here for (today is the third day with the same issue, prolly ~/> 36hrs total) . More than willing to upload other files/info as requested, but I might not be very quick to respond(or even respond at all, tbth, I refuse to feed trolls or reply to morons) but I AM reading everything posted here.

Testing_WIFI_01.ino (3.99 KB)

dashboard_CSS.txt (516 Bytes)

dashboard_HTML.txt (777 Bytes)

Does your web browser have a debug console? Maybe it’s not getting the expected result when it goes to fetch the CSS. Does the ESP8266 Web Server know that it’s supposed to return a “text/css” document for that file and not a “text/html”? Do you have any Serial Monitor output from your sketch to let you know what requests are arriving at the web server?