This guide was meant as a way to help newer players get into Touhou, all while giving additional/advanced info that can be useful in future.

Also, there may be some mistakes too, correct me if you see them.

Arrow keys move your character.

Shift puts your character in "Focused" state. While "Focused", which:
Slows down your character speed, allowing for more precise dodging,
Shows an outline of hitbox,
And usually either narrows down or changes your shot entirely, usually to "Focus" all the damage on single target.

Z allows you to shoot. the shots itself are affected by character, as well as selected sub-season. Also, holding Z while in dialogue allows you to skip it. How nice!

X releases a bomb/spell card, which has effects that differ based on selected character. However, the bombs usually clear screen from bullets, alongside dealing damage.

C activates "Seasonal Release", mechanics for which will be explained later.

esc, just like in many other games, pauses the game.

R allows to restart game from beginning when paused. Really useful when you want to avoid wasting time!

ctrl allows to fast forward a replay, as well as skip dialogues when held.


P allows to take a screenshot of game, and puts the screenshot into %appdata%\ShanghaiAlice\th16\snapshot.

Hidden Star in Four Seasons (HSiFS) in general plays like a typical traditional Danmaku STG, really.

There are 4 Difficulty levels: Easy, Normal, Hard, Lunatic.
Difficulties vary in bullet density, speed, and amount of aimed bullets fired at you, extra midboss spellcards, as well as few examples where there may be extra enemies, such as 1st stage part after 4 big fairies.

On top part of screen, there's a small invisible line, going above which will auto-collect all items on screen, alongside collecting everything at it's max value. As a note, bombing also triggers auto-collection too.

Bombs are limited-use universal tools, that usually clear the screen from bullets on screen alongside dealing damage to things, auto-collecting all items on screen and giving player i-frames to work with. Bombs also can generate seasonal petals by deleting bullets.
They are represented by stars, right below the lives counter on HUD.

Player starts game with 3 bombs, and getting hit resets bomb stock down to default value. So, if you feel like you are about to get hit with decent amount of bombs in stock... don't be afraid to bomb! Or... Just go ham with bombs on stages to auto-collect + increase seasonal release level, also a choice.

Bombs are earned mostly in fragments, that you get from bosses/midbosses after clearing attack, providing you don't bomb or get hit. However, Stage 2/3/4/Extra midbosses allow you to earn a bomb after clearing them
(note, you get spell fragment from stage 3 midboss only if you get hit. And, on stage 4, there's a big fairy that drops spell fragment if you got through the post-midboss section without bombing or getting hit. Also, on 6th stage, there are 5 big fairies at end of stage, each one dropping bomb fragment upon dying.)

Also, after getting hit, there's short time window of around 8 frames, in which you can "deathbomb", losing one bomb instead of life.

Treat bombs as universal tool, that allows to get through troublesome patterns, cancel hits, or on some characters even as a advanced scoring tool. And remember: a bomb that has not been used is a wasted bomb!



Lives represent the amount of hits you can take before game over-ing.
You start game with 3 lives, and getting hit by a bullet causes you to lose a life. As a note, bullets hitboxes are smaller than their actual sprites for most part, so that seemingly "impossible" pattern is actually slightly easier than you think.

Extra lives are earned from 2 1up pickups, one on stage 3 (providing you don't get die or bomb during midboss section) and stage 5 midboss, as well as reaching certain score values.
In base game, "extends" are awarded at 5, 10, 20, 40, 70, 100, 150, 250, 500 million and 1 billion score.
For extra, it's 10, 20, 40, 60, 80, and 100 million score instead, alongside extra stage midbosses dropping both additional extend and bomb to use.

Losing a life also causes you to lose 0.50 of your total power, alongside 0.07 power being around to collect.

After losing all lives, there's an option to continue. using a Continue:
Puts you at full power,
Sets your resources to default,
Removes ability to get a good ending, as well as save replay of current run,
Extra stage has no continues.

In general, i suggest using continues only for unlocking stages to use in stage practice mode.



Sub-Seasons are a universal tool for increasing damage output, clearing bullets and scoring.
You can select one out of 4 sub-seasons before starting your run (in extra, your subseason is locked to extra-exclusive one).

These provide additional firepower, which has 6 levels, with each level increasing seasonal release duration, range and "options" behind your character, that can be "charged" by collecting "seasonal petals". Also, the higher the seasonal release level is, the more PIV (Point Item Value) you get per bullet.

Seasonal petals can be earned by destroying enemies (note, killing enemies the moment they spawn gives you extra seasonal petals), clearing boss attacks, and most importantly, grazing bullets.

Note, that if you had any i-frames, such as ones that you get after losing a life, and used seasonal release, those i-frames will be gone.

Reimu: Homing petals that narrow down their range when focused.

Spring (Reimu's sub-season weapon): Slower homing petals from your back that also deal less damage. However, release has a huge range, and you get a lot of i-frames to work with after releasing.



















Cirno: Wide and wild icicle spread that narrows itself down when focused.















Summer (Cirno's seasonal weapon): bunch of icicles from your back that pretty much cover the entire screen with cheap chip damage. Release, while being really short, consumes only one seasonal release level.














Aya: narrow shotgun for unfocused, and piercing shots for focused.




















Autumn (Aya's subseason): Options that spawn either besides you or below you, depends on release level. Release field itself follows your position and increases your movement speed by 50%.


















Marisa: spread-out lasers that narrow down to fairly deadly beam when focused.















Winter (Marisa's subseason): a single laser below your character, and release is one small field that has decent duration. Oh, and you deal 50% more damage when under release effects too!


















Dog Days (Extra Stage subseason): a strong shot from your back, that has release that works similar to summer, but instead it goes down.

Some advanced info on shot types, alongside some little tricks either i or other people have found. Also too lazy to go into sht files and find frame damage caps :p

Notes:
The release cooldown time is 45 frames, which starts after the release ends (the release circle disappears).
At 0 power, Damage of all characters is 16*2*20 = 640.



Reimu:
1 Power - 14*2*20 + 156 = 716 total Damage.
2 Power - 14*2*20 + 144*2 = 848 total Damage.
3 Power - 14*2*20 + 120*3 = 920 total Damage.
4 Power - 14*2*20 + 108*4 = 992 total Damage.
Bomb duration - 290 frames.
Bomb damage - Spin - about 3000, Explosion - 2300-2800
Movement speed - 4.5 unfocused, 2.0 focused.



Spring (Reimu's sub-season):
Lv1 - 8*6=48 Damage, 41 Frame duration, 91 i-frames.
Lv2 - 4*6*2=48 Damage, 44 frame duration, 94 i-frames.
Lv3 - 4*6*3=72 Damage, 47 frame duration, 97 i-frames.
Lv4 - 4*6*4=96 Damage, 51 frame duration, 101 i-frames.
Lv5 - 4*6*3 + 3*6=90 Damage, 51 frame duration, 101 i-frames.
Lv6 - 4*6*3 + 3*6*2=108 Damage, 51 frame duration, 101 i-frames.

Always deals 60 damage on everything that has gotten caught itself in release field.
Note, due to big amount of after-release i-frames, it has a decent potential in scoring (almost 1.7 seconds of i-frames after release starting from level 4!), even though it may be a little bit risky to perform.



Cirno:
1 Power - 14*2*20 + 105*2+28*2=826 total Damage.
2 Power - 14*2*20 + 105*4+56*2=980 total Damage.
3 Power - 14*2*20 + 105*8=980~1190 total Damage.
4 Power - 14*2*20 + 105*12=1320 total Damage.
Bomb duration - 380 frames.
Bomb damage - 5250.
Movement speed - 4.0 unfocused, 2.0 focused.

Note, Due to how Cirno's shot works, most of your actual DPS will be the base shot.
Also, when at bottom side of screen, you can use your bomb and move upwards to graze incoming bullets with i-frames to farm releases.



Summer (Cirno's sub-season):
Lv1 - 15*4*2=120 Damage, 61 frame duration, 9 i-frames.
Lv2 - 15*4*2*2=240 Damage.
Lv3 - 15*4*2*3=360 Damage.
Lv4 - 15*4*2*4=480 Damage.
Lv5 - 15*4*2*5=600 Damage.
Lv6 - 15*4*2*6=720 Damage.

Always deals 60 damage on everything that has gotten caught itself in release field. Frame duration and amount of i-frames are same for each release level. Also due to how spread out the options are + frame damage cap, you'll mostly likely won't be able to fully utilize them. Unless, of course, you find decent way to cosplay facehugger from alien...
Release also, as i said before, consumes only one level at a time, so it's possible for seasonal release to potentially return an entire level worth of release.



Aya Unfocused (all shots hitting the target):
1 Power - 14*2*20 + 12*12*2=848 total Damage.
2 Power - 14*2*20 + 12*12*3=976 total Damage.
3 Power - 14*2*20 + (10+3*11)*12=1032 total Damage.
4 Power - 14*2*20 + (9*2+10*2+11)*12=1080 total Damage.
Bomb duration - 370 frames.
Bomb damage - 5958.
Movement speed - 5.5 unfocused, 2.0 focused

Aya focused:
Due to the way ZUN's engine handles piercing projectile, here's a graph of Damage at each power level. Basically, the piercing projectile damage gets calculated based on how much time the projectile has spent inside enemy hitbox. Or maybe something related to projectile's distance, i don't know.

Autumn (Aya's Sub-Season):
Lv1 - 16*5=80 Damage, 71 frame duration.
Lv2 - 13*7.5*2=195 Damage, 86 frame duration.
Lv3 - 12*7.5*2 + 8*5*2=260 Damage, 101 frame duration.
Lv4 - 12*7.5*4=360 Damage, 121 frame duration.
Lv5 - 8*5*2 + 12*7.5*4=440 Damage, 141 frame duration.
Lv6 - 12*7.5*6=540 Damage, 161 frame duration.

Always deals 30 damage, and always gives 29 i-frames after release.
Note, cannot deal full DPS to one specific target due to how shots are spread out unless at level 1. Level 1,3 and 5 offer best offensive utility against single targets too.
After activation, release field follows your position, Its range increases instantly at first, then shrinks.
Your own movement speed is increased by 1.5 (50%, the acceleration effect starts and ends one frame later than the release) too.
Also, if there are enough bullets on screen, you can delete enough bullets to get a level 1/2/3 charge, allowing to chain releases. Release itself does not protects you from running into enemies and has only 0.48 seconds worth of after-release i-frames, so be careful when rushing into bullets.



Marisa:
1 Power - 15*2*20 + 300=900 total Damage.
2 Power - 14*2*20 + 225*2=1010 total Damage.
3 Power - 15*2*20 + 150*2+225=1125 total Damage.
4 Power - 15*2*20 + 120*2+225*2=1290 total Damage.
Bomb duration - 380 frames.
Bomb damage - 6060, cannot shoot while bombing.
(Three layers stacked inside, middle and outside, each layer deals 2020 damage.)
Movement speed - 5.0 unfocused, 2.0 focused
Highest DPS out of all shot types.

Winter (Marisa's Sub-Season):
Lv1 - 5*15=75 Damage, 61 frame duration.
Lv2 - 7*15=105 Damage, 101 frame duration.
Lv3 - 9*15=135 Damage, 141 frame duration.
Lv4 - 11*15=165 Damage, 181 frame duration.
Lv5 - 13*15=195 Damage, 201 frame duration.
Lv6 - 15*15=225 Damage, 221 frame duration.
Always has 29 after-release i-frames.
Always deals "13+ Shooting Damage" damage when anything gets in release field (?).
During the duration, the frame output limit is increased from 60 to 90 (?), and the shooting power is increased by 1.5 times. So uhh, extra damage i guess?

It only has one laser. New lasers are generated as you level up, and old ones are destroyed when you stop firing (getting power up, talking and stage clearing will force a stop).
Therefore, if you level up from Level 1 to Level 6 without stopping shooting or getting interrupted by any of above methods, you can get 6 lasers stacked together, dealing 75+105+135+165+195+225=900 Damage in total (note, frame damage cap may reduce damage.)
While release field is fairly small, duration is decent, and low damage allows to milk PIV out of bosses like crazy, especially when paired with characters whose bombs allow grazing with i-frames.



Dog Days (Extra Stage subseason):
Lvl 1 - 15*20=300 Damage
Lvl 2 - 15*20+13*20=560 Damage
Lvl 3 - 15*20+(13*20) * 2)=1600 Damage
Lvl 4 - 15*20+(13*20) * 3)=1080 Damage
Lvl 5 - 15*20+(13*20) * 4)=1340 Damage
Lvl 6 - 15*20+(13*20) * 5)=1600 Damage
Release duration always lasts 71 frames,
Always deals 60 damage,
And always has 9 i-frames.
Just like Summer, uses 1 level per release.

to find amount of time that specific action takes, divide amount of frames (for example, 8 frame deathbomb window) by game's framerate, which is usually 60, unless your system either struggles to run the game, or you used mods to increase framerate cap for extra challenge:

8/60=0.13333333333, which gets rounded down to simply 0.13 seconds.

Point items (which are represented by blue squares) well... Give you points! Oh, and their value can be increased via seasonal releases too, up to 500,000.

Power items (who have the red squares with "P" on them) allow your character to power up, increasing range/damage. Max amount of power you can have is 4.00, and at max power Power items act the same as Point items.
(fun fact, During Okina's Stage 6 final spell card, your power is locked to 0.00!)


Both Point and 4.00 Power items have their value affected by height, from which they are being picked.

To collect items at full value, you need to:
Use seasonal release, as it auto-collects all items on screen for release's duration.
Go above POC (Point of Collection) line.
Use a bomb, bombs have same effect as seasonal releases but only for a couple of frames instead of release's entire duration.
Go into dialogue, it auto-collects all items on screen.

Point items collected even a pixel below the POC will be worth around 75% of their value.
Point items collected at the bottom of the screen are worth around 25% of their value.

The value of Point and Power items is also affected by Point Item Value. It starts at 10,000 and can be increased up to 500,000 via seasonal releases.
The following screenshot below shows Stage Clear screen, alongside Point Item Value at it's maximum possible value:



Grazing is an act of bullet passing dangerously near character's hitbox. While bullets can be grazed only once, Lasers allow themselves to be grazed multiple times through their duration.

In Hidden Star in Four Seasons, grazing seems to not provides any score increase, HOWEVER grazing makes bullets produce seasonal petals, which are important for scoring due to them allowing for high level seasonal releases.
Season items also give 10 points on being picked up too.


As i said, Seasonal releases cancel bullets, alongside an effect of turning those bullets into green items, which do increase your Point Item Value.
The higher release level is, the higher the PIV increase per bullet is:
Level 1 - 5
Level 2 - 10
Level 3 - 20
Level 4 - 30
Level 5 - 40
Level 6 - 50
Green items also give you 10% of current Point Item Value, regardless of release level.

The following photo below shows a bunch of green items heading towards character after properly timed Winter release:



Spell Card bonuses are Score-Based rewards for not dying or bombing during spell cards (using seasonal releases is allowed), which is represented by "BONUS" below spell card name. Spell card bonuses use this calculation:
1 million * stage number * difficulty value
With difficulty values being:
Easy - 0.5
Normal - 1.0
Hard - 1.5
Lunatic - 2.0
Extra - 1.0 (extra is considered to be 7th stage)
Spell card bonus also decreases over time except for Okina's Extra Survival spell-card, but this is not really that important.
You also may see people often drop boss health to low levels, and then end spells as spell timer reaches low values. This is often used to milk graze/PIV out of spell cards.


Clear bonuses are score-based bonuses you get for clearing stages. Stages 1-5 use following calculation:
(stage * 1 million)
Nothing really interesting really.

There's also a Game clear bonus. This one gets obtained after Stage 6/Extra:
(E/N/H/L: 6 million, EX: 7 million) + (5 million * lives) + (1 million * bombs)
Basically, more lives/bombs you have at end of game, the bigger the bonus is.

1: Touhou wiki.
https://en.touhouwiki.net/wiki/Hidden_Star_in_Four_Seasons/Gameplay

2: Chinese Touhou wiki, this one has more advanced info.
https://thwiki.cc/%E6%B8%B8%E6%88%8F%E6%94%BB%E7%95%A5/STG%E6%9C%BA%E4%BD%93%E8%AF%B4%E6%98%8E/%E4%B8%9C%E6%96%B9%E5%A4%A9%E7%A9%BA%E7%92%8B
(URL is a little bit messed up but should still click and work perfectly fine.)