Hello Marrow player and welcome to this "brief" but hopefully somewhat enlightening post to explain and guide you through some of the more general quirks and nuisances of the game and set you on a successful quest to save your friends beneath the mountain and slay the wretched, cosmic entity which dwells at its deepest pits. Think of this as a rudimentary Manual of sorts.
First off, let's get this out of the way. Yes your controller works fine, and no, there is no Menu screen. Everything you need to know as a player is either visible on your character's sprite, accessible through button presses or on your HUD. This also means there is no pause button, however there is an easy way to quit back to the title screen and is explained on the "Controls Info" screen on the main menu. (NOTE: This function is disabled in the Echo Realm and during Survival mode)
Also, your HUD works, but it is a consumable. Checking your Grit/Clarity (Health/Magic) is limited to only one check at the start of the game, once consumed it will not be replenished until you save. However, the number of checks you have increases with each Orphan you save, which would leave you with 14 checks one you've saved them all.
NOTES ON ENEMIES
Though it may look like a traditional 2-D action adventure game akin to something like Symphony of the Night, unlike those games enemies don't have any purpose beyond one, to stop your progress and kill you. They give no EXP, they drop no items and will never drop anything similar to an energy or magic pellet.
What this means is you can avoid fighting it is in your best interest to do so. And if fighting is inevitable, stand back and observe their behaviours to figure out when best to strike, and don't be afraid to run away.
Gung ho is no way to go.
PRO TIPS
Here's a useful tip: When faced with a gang of enemies who seem to be hitting and stun-locking you into submission, try a Backdash. Getting hit while Backdashing will propel you a long distance in the direction you were moving. This helps push you out of any relentless mobs and frees you up to make your escape.
Remember the jump and double strike rule. Jumping and attacking an enemy just before landing will give you the opportunity to attack much quicker than if you attacked twice only on the ground. A useful trick in a lot of 2-D action games including this one.
SEQUENCE BREAKING
Certain parts of Marrow's world have a hard wall which prevent you from pushing forward and exploring a certain area until a requirement has been met, however, most of the game does not have such walls. Some areas have soft walls and most have no walls at all. This means that theoretically you can push into new areas without fully exploring the area you are in. Instead of a wall as your barrier you will find the cold realization of being in way over your head, unprepared and unequipped for this new area's threats and puzzles, and finding that the journey back won't be so easy.
The Onus is put on you, the player, to do your due diligence and decide if you truly are ready to press on and have fully explored the current area. Consider this an unshackling from way points and direction, an emancipation of your player agency.
ON SOFT WALLS
Soft walls are objects in the game that discourage but don't fully prevent your progress as a player. For example, an energy barrier protects the room containing the first Boss, however this barrier is not an impassable wall. If you choose to (and have the Health for it) you can backdash into it and make it into the room containing the Boss WITHOUT ever finding the means to destroy the barrier.
The damage the barrier does is very significant, and be forewarned, the barrier will still be there even if you beat the boss and you will never survive a second hit from it, so your only option is to move forward, into a place you may not be ready for. (Don't worry, there is another way back.)
This is just one example out of a few where seemingly crucial barriers can be circumvented by using these soft walls, even an entire boss fight can be circumvented without missing anything crucial, just be prepared to pay the price for your ambition.
ENDINGS
Marrow features two possible endings which are dependant on whether or not you have found all of the lost orphans. They are well hidden and some objectives will require a careful eye and a memory of the game's background environments. Don't worry though, getting the bad ending simply means reloading your save and scouring the depths for the kids, you won't be locked out of anything just for completing the game.
SURVIVAL SCORING
Survival is a mode which opens up after completing the game (either ending) and tasks the player with beating the game with a set number of lives, gaining lives by rescuing the Orphan dolls (replacing the Orphans), beating bosses and getting items to tally up your score, which you will only receive upon finishing the game. No "you tried" stickers for anyone.
The system for scoring is never properly explained in game so let me break it down in general terms.
The game Starts with a set score which depletes with each passing second of playtime. The initial score is substantial and you're given a hefty amount of time before the score reaches zero so you don't have to be in a big rush but time is a factor.
However, rushing through the game to get straight to the final boss is also unwise since the final score is tallied based on a number of factors including how many items you have. Beating Bosses adds to your score (stronger bosses add more than weaker ones) but more importantly each Max Item total for Grit and Clarity is multiplied by 100000 at the end of the game making it an important part of getting a high score.
The number of lives you have is an even bigger factor with that number (the number of lives remaining) being multiplied by 325000, so finding the Orphan dolls, and most crucially, not dying, are also major factors in the scoring system.
SMALL BUG
If you die a the very beginning of the game (before the first savepoint) and reload back in the attic your controller may not immediately respond. This can be fixed by simply pressing B on the controller (or Y or RT). This should reset the controller back to its regular behaviour.
Well that about covers it. I hope this small guide helps you on your journey.
If you wish to read more about the game and read some small lore tidbits as well as some enemy breakdowns then check out the games Dev Log here:
https://forums.tigsource.com/index.php?topic=57659.0
Good luck down there!