The core gameplay loop follows a very simple mechanism

Kill enemies, collect the gems they drop to level up, select an option at level up to help in offense or defense, and repeat while avoiding contact with enemies.

However, the options at level up are not all intuitive, and there's a major disparity between things that help significantly, and things that don't help at all. So, I've put my observations together into this guide.

Transformation requires a lot of kills while receiving no damage. As that happens, the bar just above the item list will fill. Each level increases your base stats, so it's a good idea to try to maintain a high transformation level as much as possible.

The options that appear in the level up window are heavily skewed towards whatever has been upgraded the most in the shop.

A player may notice that different modifiers might be available in different runs even when choosing the same weapon.

The reason for this is because the order the weapons are chosen in matter:

• The FIRST weapon will receive ASSASSIN modifiers
  
• The SECOND weapon will receive SENTINEL modifiers
  
• The THIRD weapon will receive WARRIOR modifiers

This means that each weapon has three different sets of modifiers for it.

Alright, with the mechanic of how the modifiers work out of the way, let's get into the core of this guide -- Weapon details and tier list.

Tier List

• S - Tornado (Sentinel), Chain Lightning (Assassin)
  
• A - Purification Aura (Sentinel)
  
• B - Shuriken (Assassin or Warrior), Dark Fire (Warrior), Chain Lightning (Warrior), Tornado (Warrior)
  
• C - Shikigami Frenzy (Any), Incendiary Talisman (Any), Tornado (Assassin)
  
• D - Purification Aura (Assassin or Warrior), Dark Fire (Assassin)
  
• F - Lightning Barrage (Any), Crushing Boulder (Any), Chain Lightning (Sentinel), Dark Fire (Sentinel)

Note: weapons are listed multiple times for their modifier interactions. If playing without using modifiers, ignore the duplicates.

Individual weapon analyses and explanations are as follows

Easily the best weapon in the game. This weapon keeps enemies away, minimising risk to almost nothing, and outperforms any other weapon even without modifiers. Easy to double down on the safety by making use of the Sentinel modifiers increasing the aoe life and knockback.

Pros:

• Heavy knockback
  
• Long aoe life
  
• Wandering aoe with no aim required

Cons:

• Collecting exp is harder with all the enemies thrown to the edge of the screen. That's it.

A very powerful weapon at higher levels. Although the auto-targeting can be annoying to work with, and generally doesn't target bosses, the raw damage and range is rather impressive.

Pros:

• High damage
  
• Long range
  
• No aim required

Cons:

• Only shows its value at higher levels, minimum 2
  
• Bosses are lower priority on the auto target, meaning it generally doesn't hit bosses
  
• Sentinel modifiers are nearly ineffective with Chain Lightning
  
• Only acquired after getting it in Stage 3 from the middle row, left room special chest

Deceptively powerful, it doesn't appear that good at level 1, but it effectively forms a constant shield-like aoe starting from level 3. Good knockback and consistency make it a good defensive choice.

Pros:

• With Sentinel knockback modifiers, can keep most enemies away passively
  
• Reasonable damage over time -- rapidly hits enemies over and over again despite low damage values
  
• Constant aoe starting at level 3

Cons:

• Nearly unaffected by Assassin and Warrior modifiers
  
• Doesn't help very much with bosses

Although the weapon looks very underwhelming, it's surprisingly useful. Reasonable damage and prioritises targets based on proximity, firing at the closest enemy to you. Can ricochet and potentially multi-hit the same target. Solid weapon choice.

Pros:

• No aim required
  
• Very high accuracy
  
• Solid damage
  
• Rapid fire at high level

Cons:

• Visually unappealing
  
• Hard to feel its effectiveness until the end screen
  
• Sentinel modifiers are nearly ineffective with Shuriken
  
• Only acquired after getting it in Stage 3 from the top row right room special chest

A classic move for a kitsune, the fire doesn't offer near the same degree of protection as the purification field. However, it synergizes with the purification field well due to their aoes overlapping, leading to a lot more damage loaded at the edge of the aoe.

Pros:

• Good damage
  
• Hits rapidly at high levels due to the number of projectiles
  
• Synergizes nicely with Purification Field to maximise damage near the edge of the aoe

Cons:

• The animation for the dark fire leaves an opening where none are active at regular intervals
  
• It only really gets effective at high level when more projectiles are in play
  
• Modifiers are a bit unintuitive for it - area increases the size of the flames, not the radius they orbit in

This is where the weapons start getting too mediocre to use. Though, arguably Dark Fire is the start of the mid-point. Shikigami Frenzy isn't too bad, but it leaves a bit to be desired. Although it can do good screen coverage in the beginning, it falls off hard as a stage progresses due to its abysmal damage. It also seems to fire in random directions at times, rather than at an enemy.

Pros:

• Good early game due to no overkill -- letting projectiles spread to hit more things
  
• Projectile amount and spread nearly guarantees they'll always hit something

Cons:

• Terrible damage
  
• And for good measure, let's put that again to emphasise the point -- terrible damage
  
• Unreliable auto-aim
  
• All projectiles from one burst will go in the same direction for the duration of that burst. No adjustments if there's no more enemies in that direction

Arguably better than Shikigami Frenzy, but still in the same category. Auto aim seems random, making it unreliable to use even if it has better damage. But it's worse due to fewer projectiles in play, making the auto aim even more impactful.

Pros:

• Can do reasonable damage

Cons:

• Unreliable auto-aim
  
• Projectile life and speed doesn't allow for ricochet off the edge of the screen like the Shikigami Frenzy can do
  
• Low projectile speed
  
• Wide spread and unreliable aim prevents strategic use

Despite their good base damage, they belong in the trash. Unreliable aoe, offers no protection, and fire speed is slow at low levels which reduces their effectiveness even more.

Pros:
What pros?
Cons:

• Unreliable auto-aim
  
• Small aoe
  
• Enemies don't generally group up enough for the aoe to have effective hits even if the auto aim works
  
• Slow to fire
  
• Even worse at low levels

It's a good idea to avoid upgrading the katana altogether where possible - it doesn't scale well and none of the modifiers drastically help.

• Forceful Blows - Even with bad scaling, the katana can still provide a slight defense by helping keep enemies away
  
• Swift Assault - Faster attacks means more swings in the same amount of time
  
• Wide Swings - Although conceptually helpful by letting the katana hit more, it has the drawback of making the space behind the blade wide enough to allow some enemies to get free hits in
  
• Empowered Strikes - A damage improvement on a weak weapon helps but can't help it scale
  
• Critical Impact - The katana's poor critical rate and damage makes the benefit of an improved critical multiplier unnoticeable

Works best with Shuriken and Chain Lightning. These modifiers primarily focus on improving damage.

• Life Leech - HP recovery from Life Leech is a huge benefit, especially from weapons that hit rapidly or multi-target.
  
• Swift Ambush - Weapon speed lets more things be hit more often, good modifier.
  
• Shadowstrike and Ruthless Ambush - It's hard to determine the exact value of these critical modifiers, but they synergise well and can be noticeable. If only taking one, Shadowstrike is the one to take
  
• Lethal Projection - Standard modifier, increases damage. Hard to tell by how much though
  
• Pinpoint Precision - Accuracy doesn't seem to have any mechanical benefit or drawback in this game. This modifier doesn't seem to do anything noticeable as a result.

Works best with Purifying Field and Tornado. These modifiers primarily focus on knockback

• Thump - This modifier is amazing - it seems to bypass the knockback chance and automatically applies knockback
  
• Battle Vigilance - Reduced cooldowns works extremely well for most weapon -- HOWEVER, do not take with Dark Fire or Purification Field as both are constant effects already
  
• Wide Sweep - Bigger aoe is better aoe
  
• Unstoppable Force - Larger knockback synergizes really well with Thump
  
• Lingering Presence - Longer lasting works well with Tornado, but also doesn't work with Dark Fire or Purification Field
  
• Forceful Impact - Unneeded if using Thump

Something of a catch-all for the other modifiers. Several range/size effecting modifiers

• Add Fire - Does not work with all weapons, but for a few of them this modifier creates lingering flames on the ground that deal damage to other enemies
  
• Battle Readiness - Faster cooldown means more and faster attacks, good to use
  
• Hasted Projectiles - Increases the effectiveness of weapons by letting the shots hit more/faster
  
• Expanding Fury - Increases the aoe size, helpful to deal more damage to more things
  
• Battleborn - Can't go wrong with more damage, but there are better modifiers
  
• Sweeping Strikes - Range doesn't matter for most weapons. However, for Dark Fire, this should be taken over Expanding Fury

Dash unfortunately has many not-useful modifiers. Though that does make preventing the unused ones from appearing easier by simply never upgrading those in the store

• Agile Recovery - Between high level Dash and Agile Recovery, it's almost possible to chain dashes without the multi-dash modifier
  
• Continuation - The damaging blast from Dash can be effective in how much it does, making continuation almost turn Dash into a 5th weapon
  
• Double Take - Not entirely needed if using Agile Recovery, but it can still be useful for the immediate chain
  
• Elusive Movement - The description is misleading, because this modifier actually increases the distance of each dash, making it deceptively useful
  
• Swift Evasion - Lets you reach the end of the dash sooner, which helps with kiting
  
• Forceful Dash/Wild Escape - They might not be that bad, but they're overshadowed by all the other modifiers

All these modifiers are good, but they still have a priority to them

• Just Go Down - The most important modifier for the ultimate -- it lets the ultimate kill most bosses in the game
  
• Reap Rewards - The magnet effect is useful to collect all exp at once, however it requires a high level modifier to be helpful
  
• Clean Reset - The hp recovery can be useful if Life Leech doesn't appear, but otherwise it's unneeded

Due to how there is a secondary level up from not taking damage, half of the passives in the game are not particularly good.

As a result, this tier list is rather one-sided

• S - Head Hunter - more money means faster upgrades in the shop, and money provides for continues and level up rerolls
  
• A - Gem Senpai - more exp means more and faster upgrades in a run, which can make a significant difference it it lets you upgrade a weapon to high level fast
  
• B - Nimble Steps - not entirely needed if using Dash effectively, but there's no denying this passive is almost as good as Dash for mobility
  
• C - Magnet - increasing the pickup radius is never a bad thing
  
• D
  
• E
  
• F - Fortitude, Healing Pulse, Bushido Button - Since the secondary level mechanic requires taking no damage for a long period of time, none of these are actually helpful in the long term

While many builds can handle normal enemies, most of the weapons don't handle bosses very well.

Thankfully, none of them need to with the boss damage multiplier for the ultimate.

The system itself is intriguing, with the modifiers potentially allowing weapons to be built differently rather than always behave the same. In execution, however, there's a significant disparity between what modifiers are worth getting, if any, and just simply getting the weapon as high level as possible.

This guide/tier list is provided as-is, and likely won't see any further updates.