Here's how I beat Classic mode. (Right to the point, baby!)
First of all, I would recommend that you use the Radar, but not too much. The Radar is a good tool, it shows you where any orbs are, and it has other purposes too. But do not only use the Radar to figure out where you are or how to get around since it may show you walls or hallways that aren't really there so be careful. Now we know what's going on (for the most part), we still have an issue, being the monster himself! Legs (the monster) is the only thing that can kill you, with one exception but that isn't important as it's really rare.
Here's how Legs works and can be fended off!
Legs can randomly spawn nearby, usually in intervals after you scare him off. So, how do you scare him off then? All you need to do is simply look in Leg's direction, and flash him in his big, red, goofy ahh eyes and he's book it faster than a rage-quitter after getting hit by one combo in a fighting game. But like said rage-quitter, he has more tricks. Being that he can show you his true rage.
After around, roughly, 2-3 times of scaring him off, he will stand still and stare at you with a prompt on the screen saying 'Run'
And just follow the rule, run for your life and avoid any dead ends as he pursues you.
Here is how to get away from his wrath.
First of all, take as many turns as you can, this'll make him lose sight of you. This is important since as long as he can see you, he will never give up.
And that's basically it. But you'll only need these tips once per run. Why? Because if you enter the Run phase a second time, he will always get you.
The map is, I think please don't DM me on Discord if i'm wrong, always the same each run. I'm unsure if the orbs are also in the same place but never the less.
The orbs, on the other hand, are relatively simple. There are around ~20 orbs in the maze which you need to collect, pac-man style (or I guess Dark Deception style?).
So, here's a TL;DR. The map is the same every run but you spawn in a different spot and there is a monster you scare off with your flashlight and will chase you after a while but will kill you if he chases you twice. The main goal is to collect all ~20 orbs to win!
I hope you found this guide helpful!
StrikareaY, out!