Having completed the game to a self-acceptable level (unlocked the full gallery and all outfits through either achievements or keys, completed the Cakeiary, with all bosses defeated with every girl), I have to say...

This game, while starting out incredibly enjoyable and fun, eventually just completely dropped the ball when it came to the gameplay loop, rewards, mechanics.
Sure, some of it can be chalked up to me not having the skills for such a game, but honestly, just TRYING to complete the Cakeiary had made me confront all the issues enough times to confirm that yes, this goes beyond skill issues.

To start with the good: everything, from the premise, the general design of the girls, the bosses, the toggleable voice, gas and gurgles, the alternative outfits and character models were fantastic, and I genuinely think that all the effort that went into the game is a testament of the creator's effort and creativity. I found just the inclusion of braps as welcome, considering how rarely they show up in weight gain/expansion/inflation games (with this game included, I can still count them on one hand). A good chunk of the achievements was fun to get, and the fact that you can also use the keys to unlock most of the pictures and outfits is very welcome as well.
I really liked how many of the girls' special powers worked, especially when it came to the bosses. It took a bit of practice (more on that later), but it's always entertaining and rewarding to see the different forms of defeat we can dole out onto the cake women.

Unfortunately, this is where the positive notes run out. I'll try to keep things SOMEWHAT concise and split up into a neat list, rather than wall of irate ramblings.

1. The gameplay loop
To cut it short: it's counter-intuitive, with SEVERAL frustrating features.
Having the girls grow larger is a great gameplay feature... Until it isn't. The fact that you're effectively crippling your own mobility and maneuverability and making yourself a bigger target as the game increasingly becomes a bullet hell is... Unrewarding, to say the least. It's not even a "high risk, high reward" situation, since you're pretty much encouraged to eat the cake... Balls? Pellets? Let's call them chunks. It increases your firepower (to varying degrees of effectiveness, depending on the character), which becomes a complete necessity once the armored cakes begin to show up. You're not really given an option here, and above Stage 16, the game becomes so saturated with enemy bullets that the only way to dodge them is to either have full GP and burp/fart them away, remain at minimum size and thus be able to move out of the way, or retain maximum size from the previous stage, and either slip into the background or blow up. The fact that the girls' firepower increasingly becomes ineffective at higher Stages becomes particularly painful, and the fact that the only way to increase it is through crippling our mobility and making us a bigger target (and even then, some of the girls' firing method is just ineffective to begin with). There should really be either a temporary firerate and/or damage booster item (maybe a different cake?), or have the girls' firepower just naturally become faster/harder hitting by default as the game advances up the stages, because cycling between having no effective firepower and not being able to dodge due to our size and speed, while the enemies only get stronger and stronger is really demoralizing and frustrating.

1.a. Particular Pet Peeves: Shitcakes
Never have I thought I would feel such intense animosity towards inanimate pieces of confectionery, but here we go:

FUCK THE STRAWBERRY CAKE SLICES!

They are the single greatest source of my frustrating in the entire goddam game. No matter the size I am at, they always have to be priority targets (unless there are Coconut cake slices on the Stage, more on THOSE later), due to how INCREDIBLY annoying they are to deal with. The fact that they fire at slight diagonal angle, and their shot travel slightly slower than other cakes makes a pain to deal with, especially towards the end of a stage when they slip down right above girl, and being their "Death Scroll", adding even MORE lateral movement to their shots. If you aren't at your smallest size, even ONE can become a nightmare to deal with, and more than one is typically a death sentence unless you have the GP to repel their shots. But even when they're staying at the top half of the screen, them just releasing their shots from there only ADDS to the frustrating bullet hell the game becomes.
Coconut cake slices are the bastard understudies of Strawberry cake slices. Due to their durability (and the ineffectiveness of some of the girls' firepower, even at larger sizes), they become annoying minibosses to deal with. The fact that they can take out nearby cakes is welcome, but considering how LONG it can take to kill the damn things, that explosion will likely go to waste due to all the other cakes being destroyed around them before they finally blow up.
And finally, Cheesecakes. I actually thought they were pizza pies the first time I saw them. Cheesecakes are only tolerable by virtue of not firing all that frequently, and that once enough of them is destroyed, you can easily dodge them. They take long time to get rid of, but considering they drop a chunk with each slice destroyed, and they can be more easily dodged than Coconut, but ESPECIALLY Strawberry cake slices, its actually rewarding to treat them as something of a "micro boss". They're brought down by the fact that they usually end up right next to a Coconut cake slice, and effectively become its shield, making it even more frustrating to get rid of the damn Coconut cake slices. What's even MORE annoying is that if when they spawn in during the start of a Stage, they can slip really low, and effectively fire off their omnidirectional bullets in a way that it comes at our character NEAR COMPLETELY FROM THE SIDE, DAMN NEAR HORIZONTALLY. Unless your still at a smaller size, or have the GP, you're basically fucked against these shots, because they basically attack you from an angle where you can't dodge, only back away in the vain hope that the angle of their path will narrowly miss you on the far end of the screen.

2. Character catastropheCatalogue
Silly Sally is our baseline heroine. Her shots are fairly effective, even at low levels and upgrading her firepower grants her both slightly stronger bullets and wider spread of them. Her bubblegum special is fun, and the fact that you can use it to start "gumming up" entire cake slices if you defeat a boss with it is just *chef's kiss*.
Perky Phoebe has, hands down, the most effective firepower among the girls. It only grows stronger as she grows larger, without losing too much firerate (which CANNOT be said about a certain OTHER character below). The fact that her cleavage can absorb enemy bullets is very useful... If muscle memory wouldn't drive me to dodge 80% of the time, since all the other girls (apart from Sugar with the apple power-up) have to in order to NOT DIE. The Cleavage shots are... Ineffective. I didn't notice any dramatic change, even when Phoebe started to look like she's carrying a lantern in her décolletage. Because of their ineffectiveness, they can slip out of sight and out of mind, leading to catastrophic momentary distractions when they do become active. Phoebe's milk special is kind of underwhelming, especially when compared to the other girls, but she makes up for it with variety (such as by erupting like a pair of dairy geysers if she gets to her maximum size while her special is active, or eats a milk-coated blueberry cake chunk). Perhaps, there could be something special done with eating a milk-coated Trés Leche cake, even if it just instantly brings her to her maximum size and causes her to squirt milk.
Massive Martha is okay, but is HEAVILY brought down by the aforementioned counter-intuitive gameplay loop - at higher sizes, not only does she become a massive, slow target, but her firepower also becomes so infrequent that its practically useless (especially since it DOES NOT make up for this reduced rate of fire with more damage). The fact that she automatically begins to grow if she had eaten Earthquake cake and the player has double-filled her GP to the point where its all red interesting, and can be useful for getting her up to a size where her shots (infrequent as they are) can deal some serious damage and can make short work of a boss. All in all, she could be easily made better by increasing her fire rate at higher sizes and/or making her shots hit harder.
Bouncy Bella, while a fun character to play, has the worst firepower out of all the girls (which is saying a lot considering we also have Pump Punk in the roster). Her blunderbuss-like spread is simply ineffective, even at higher sizes, and concentrating her fire, EVEN AT HIGHER SIZES, simply doesn't make it effective enough (not to mention that it slows her down, which is ESPECIALLY painful when she's at a larger size, and there's a bullet hell to dodge). Once the armored cakes come into play, she basically becomes useless, and every Stage becomes a survival round. Her Durian special is both useful and multi-functional, as her constantly filling GP effectively allows her to parry more shots (more on parrying later). One way to solve this would be to replace her birdshot-like spread with something like a crescent "wave" shaped shot, as if it was the sound waves created by her clapping asscheeks. The larger she gets, the larger and wider these waves become, with their center part hitting harder and harder, while at the same time, her rate of fire becomes slower due to the more infrequent (if more powerful) claps. This could also make her more distinct from Sally in the firepower department, as right now, she's effectively just a weaker version of Sally with a different special.
Shifty Sugar is the mechanically interesting out of all the girls, but because she can use the powers of Phoebe, Martha and Bella, she especially helped to highlight the limitations of the other girls' firepower (while also confirming that Phoebe has the most effective shots). I kinda expected Sugar to gain weight like Sally in her "flavorless" form, and was mildly disappointed that she just doesn't grow at all unless one of her three fruit cake powers is active. I also figured she would gain the ability to copy Pump Punk's power once I unlocked her, but considering the general issues with Pump Punk's entire playstyle, the fact that she doesn't gain it is probably for the best. Sugar's special is also fun, but I think her "SUPERCAKE" form could stand to last a little longer.
Pump Punk... Hooo boy. I understand why she was locked behind an achievement that you couldn't brute force with keys, but she made for a rather underwhelming reward for the effort required to get her. She's completely mechanically different from any of the other girls, and not in a good way. Her pump hitting a cake practically locks her in place (an awful idea in a game where staying mobile increasingly becomes both a requirement and a privilege), and the fact that she only grows in size after inhaling, while thematically fitting for her, throw me for a loop. Her special is also rather underwhelming, all things considered, and simply fast tracks her into becoming the next Hindenburg. The fact that the firerate of her harpoons ALSO slows as she gets larger is just a further slap to the face. Her ability to turn enemy bullets into her own projectiles is great... But it made me realize how much I WISHED the other girls could have this by default, using their GP blasts to not only parry enemy bullets, but also also turn them against the cakes. It's practically a requirement above Stage 24. And if the other girls have this ability as well, you could make Pump Punk's ability more refined by having the bullets HOME IN on the cakes that originally sent them, making it all the more satisfying to use this ability. As for the harpoon shot, perhaps, at higher sizes, it could become something like a line charge (https://en.wikipedia.org/wiki/Mine-clearing_line_charge), which becomes more and more powerful the larger she gets, making up for the slower firing speed and the fact that her using her pump to blow up cakes essentially cements her in place for the duration of the pumping. It would essentially turn her hose into one long Coconut cake slice, only with power amplified multiple times over at her penultimate size, potentially able to clear an entire stage in one blast. An alternative is to have her launch multiple hoses at once, blowing up several cakes at the same time (this could also be used for a special defeat for Caring Cheesecake, where not only her, but also, several of her cheeselings get inflated all at once).

3. Stages and Gamemodes
The aforementioned bullet hell aspect, combined with the gameplay loop can really rub me the wrong way, but above Stage 24, the game basically say "Fuck you for playing!" - if I wanted that sort of sentiment from a game, I'd play Spec Ops: The Line, where it is at least thematically fitting, and not the result of ineffective characters facing up against increasingly difficult enemies. You either have to sacrifice sacrifice yourself to return to your small base size, or you have to stock up on GP like you're hoarding natural gas for the apocalypse.
The way certain stages can fuck you over or trick you into dying, when you were trying to save up GP or a special for the boss (and the frequency at which I experienced it) had probably left me with trust issues by this point. I haven't considered myself a paranoid man, yet here we are.
As for the various gamemodes, they're okay. Mixed palette is good if you wanna finish off the Cakeiary (for the most part - sometimes, it just refuses to give me the boss I want, and keeps cycling through the alternate forms of others). Simple palette is just that. It's not really rewarding, and since you STILL have to deal with Strawberry cake slices, there's no real reprieve in it, either. "Watch your Weight!" is fun, Boss Buffet would be better if you were given your special between the bossess (it would also help with the Cakeiary), Speed Eating only WORSENS the Strawberry cake slice Death Scrolls, so no, thank you! Rainbow cake is pure gambling. Cheese It woudl've been fun if the game's incongruencies haven't eroded a good chunk of my good will.

I honestly can't wait for the full version of the game, even if it retains these very same issues!
I also must applaud you on the effort and creativity that went into this project.
Now, I WOULD suggest another character for a more thighs-focused expansion/weight gain, but considering the game already has a roster of six distinct characters to play with, and you probably heard a million suggestions like mine before, I won't bother you with it.

Keep up the good work!