Okay, so. Gonna be a bit complaex but hope you find this interesting. (note that this is real time 3D combat, not turn based or anything like that, think of Destiny, Minecraft or Witcher when reading this)
So the game has multiple things in combat (to make it easier I'll use character example) [DUR=Durability, HP=health, WP=Will Power, ATT=attack damage]:
Before you upgrade Luffy, these are his stats:
HP: 3000 STA: 150% WP: 10 000 ATT: x3 DUR: x5
Now here's a Level 1 Seaman:
HP: 50 STA: 10% WP: 20-30 ATT: x1 DUR: x1
Now here's Crocodile:
HP: 5000 STA: 200% WP: 15 000 ATT: x20 DUR: x10
Okay, so now I'll give you guys a few attacks (un-upgraded):
Gum Gum Pistol: 50 Dam, -5% STA, Gum Gum Bazooka: 200 Dam, -50% STA Gum Gum Gatling: 55 Dama/(punch or second or whatever), -10% STA/second
Slash: 30 Dam, -1% Sta
Desert Spada: 300 Dam, -30% STA Sables: 50 Dam/second, -40% STA
Alright. Lemme explain how the game works. If Luffy were to fight a Level 1 Seaman, if he hit with any of his attacks, it would be an instant KO. Why? Cause his Gum Gum Pistol does 50 Dam, thus takes away 50 HP from the Seaman, which is his full HP. Plus his ATT is x3, which means he 3 times more damage. 50x3=150. So with those stats on Luffy, the Seaman would really lose 150 HP. The Seaman's DUR is x1 which means he takes 1 times less damage, which is just the amount given meaning 150 Dam. If his DUR was x2, he'd lose 2 times less damage. 150:2=75, So if he had DUR: x2, he'd lose 75 HP instead of the intended 150 HP. If the Seaman were to attack Luffy using his Slash attack, Luffy would lose 30 HP. But since Luffy's DUR is x5, he loses 5 times less HP. 30:5=6. So he would 6 HP instead of 30. In terms of STA, if Luffy were to fight 20 Level 1 Seamen (lol), and hit a Gum Gum Pistol on each of them in rapid succession, they would all die instantly and leave him with 100% Stamina cause 150-(20x5)=100.
I'll let you deduce what would happen with Crocdile using that info.
Now for upgrades. This has two ways it can go that I'm not which one to do.
1. You need to get a certain amount of XP or SP (not sure which one) to aquire an upgrade. So if there's a health upgrade that gives you 500 more HP, you need to like 100 XP. But there's an upgrade for 100 more HP that costs 500 XP. You could grind a lot and get that +1000HP upgrade and skip the 500HP. Yoi can get these multiple times but will reach a limit. Example:
+500HP: costs 100 XP and you can get it 10 times. +1000HP: costs 500 XP and you can get it 2 times
2.Classic way of once you level up you can get a or multiple Skill Point(s) to spend on an upgrade. This has tiers and categories
Health: 1 Tier: +100 HP, Tier 2: +150 HP, Tier 3 +200 HP...
There's also the Attacks you can unlock but I'm not sure how to do it.
There's different attack types: Blunt, Shock, Sharp, Electric, Fire, Water or Liquid, Poison... Luffy is invulnerable to Blunt and Electric attacks but weak to Sharp, Shock, Electric, Fire and Poison attacks. Through upgrades, forms and buffs, you can become stronger against certain attacks. Like say if Luffy goes into Gear Third or uses Busoshoku Haki, He becomes invulnerable against Sharp attacks. If Chopper goes into Monster Point, he becomes invulnerable to all attacks. All of Luffy's and Sanji's attacks are Blunt, while all of Zoro's are Sharp. If Zoro were to encounter someone who's invulnerable to Sharp attacks, he'd be screwed. (thankfully I gave the player the abilility to switch the sides the swords face). Nami's Thunderbolt Tempo is an electric attack and Usopp's Flame Star is Fire. In some cases, there can be combined types of attacks. Like Sanji's Diable Jambe form gives him both Blunt and Sharp attacks instead of the original Blunt from his normal form.
Now for a different topic:
At the beginning of the game, Luffy, Nami, Zoro, Usopp and Sanji are available to play as and you sail with the Going Merry.
While sailing, you can do many things:
-You can go around the deck of the ship (only as Luffy though), talk to the other crew members to do things.
-Talk to Usopp to repair the ship and upgrade your stats and abilities. (but the shipwright position will be filled in once you recruit Franky).
-Talk to Nami to find the closest island and percentage of the Grand Line you've explored as well the ship's log.
-Zoro serves as the lookout, alarming you of an island or ship.
-Talk to Sanji to give you food and technically the doctor.
-You can also talk to the crew to see how they're doing, goals and feelings about the voyages as well as other things.
-Once you acquire her, Talk to Nico Robin for details on characters abilities, and for wardrobe.
-Franky for ship repairs and upgrades
-Chopper for health and meds
-Brook for background music
-Other places you can go is the helm to navigate the ship, bed to sleep (basically skip over time and recover) and figurehead to wait it out.
You cannot play as the other on board.
On the Going Merry, two things can happen, either you find an island or fight another ship or fleet of ships. On a loot island, you can embark on the island and pillage for Gold, food and resources for your adventures. Extra islands will start a side arc where you meet extra characters and are useful for leveling up. They don't always have main enemies or sometimes, even enemy soldiers and can sometimes be a string of conversations. Sometimes, they could house defeated bosses or new bosses you've yet to meet. Important islands, like for example Alabasta and Skypiea, will start a main arc where you fight a new main enemy like Crocodile and Enel and their subordinates Baroque Works and God's Army respectivelty. During these arcs, you can unlock upgrades and abilities to use in your battles. During a main arc, important things that affect the rest of the game will happen like acquiring a new crewmate or getting a really high bounty or hearing of new people.
There's also ship combat.
To be continued.