The basics
Castle Fight is a rather simple map to get started but with plenty of depth to dive into later. The premise is simple, you're just a worker and so are your 2 allies, you're tasked with destroying the enemy castle, while defending your own. In an event of not being able to destroy your enemy, the win is decided by who has more Rescue Strikes remaining or in case of a tie, income. There are 3 main way of fighting your opponents: unit spawning buildings, spell buildings and shop items. Those ways are meant to support one another, how you use them will be the key to victory. This guide's aim is to make you familiar with the basics, without overwhelming with detail and should serve as a quick reference to get started with your games.
The worker
The worker is the core of your gameplay. What worker you have determines what race you have, each race has their own set of unique buildings. The one exception is the Ultimate Builder which is exclusive to the Ultimate Mode (-um) where all your buildings are randomised. For this guide we will not be focusing in this unique worker. The most important feature of the builder is of course buildings, which can then be placed within the walled off areas near your castle. Your worker is unable to leave this area. It is recommended to turn on grid to be able to more easily place buildings. The 2nd most important feature is the Rescue Strike. Every worker/player has one, it is a big aoe that kills all enemy units within a big AOE. Be mindful it must be close to your worker. How you handle this skill is extremely important. Your worker has 2 other features, an ability to cast a free blink in the castle area to better move around and the ability to access a shop. You shop either by pressing the shop on your worker or clicking the castle.
The resources
There are 2 resources in Castle Fight - gold and lumber. Gold is earned from kills and from passive income (how it is calculated will be a subject of a whole another guide) and is used to purchase just about everything. Lumber is generated based on the amount of gold spent on buildings. It is used more rarely than gold, only for special buildings, legendary upgrades and some items but is nonetheless important as what you get for it can often turn the tides of battle.
The Rescue Strike
The skill of such importance must have its own section. In the current version of the game, if none of the castles get destroyed before the round end, the winner is decided by the count of remaining Rescue Strikes (or in short "RS"). A tie in strikes means that income will decide who wins the round. Due to these reasons, you do not want to strike without purpose and avoid accidentally "double striking", which means using the skill at the same time as your ally. First and foremost, it is very much advised to ask who will RS before a need occurs to avoid panic, in case you do not want to ask, simply communicate that you will strike. Usually, the reason to strike is a big enemy army coming with no other way to defend, in which case you will try to remove it at a right opportunity. There are a few elements to consider, importantly you do not want to lose your castle or ANY buildings. Ideally you strike when your army is coming or soon to spawn, not after it is dead. You can strike anywhere from the entry to your castle area to the back where your castle is, you have to judge whether its good to strike quickly or wait for enemy units to group up better depending on how threatening their army is. Lastly, be wary of striking too late, in certain situations the enemy army might split into 2 smaller armies, in which case your RS will not kill all units.
"Normal" buildings
Normal buildings is one of many ways to refer to any and all buildings that spawn units to fight for you. This is your bread and butter so be careful, choose a barrack that spawns a unit that will help you win. The units often serve different roles: anti-air, tank, dps and many more. Choose the right unit based on your enemy (magic damage to kill heavy armour) or based on your allies (if they went with a tank, a dps or support might be nice). It is strongly recommended to build with your allies, most often in the top, back side of the castle area. Building too far at front or on the other side (in this case: bottom) can split the enemy army or leave your units to die alone. There are 2 additional features for the barracks: synchronising (it is a spell within the building), which allows you to have units spawn at the same time and setting the spawn point (select the building, then right click somewhere), allowing to spawn units from the building at different sides of it. The last thing to consider is specific strategies you can employ with building. You can use all buildings to block pathing of your own units, possibly caging them inside, which is deceptively important. Another strategy is commonly referred to as "434" which is a specific way of building, where it maximises the use of a special building owned by the Mechanical builder.
"Special" buildings
This category includes all buildings that have unique effects. They include legendary buildings, buildings that cast spells and ones that have passive effects. This category can be focused on providing utility, buffs or damage, but usually excluding spawning units. There are a few special buildings that spawn units but the way they do it is solely unique to that building. Special buildings cost lumber and gold but do not give as much income or lumber as their "normal" counterparts. Nonetheless they are very important, you have to consider how best you can use them to win, while also considering how to counter enemy specials. The effects vary wildly, so you have to learn how to use them on case by case basis but be wary, building too many or too little can be equally bad for your team.
The towers
A rather simple category of buildings. They are built in your base and used to defend. Can help you survive a tough early game but be very careful, the enemy will counter them with siege units that can remove towers surprisingly quickly. Not every race has it and some are stronger than others. They cost lumber just like special buildings so remember that it will delay you getting to some special buildings by that cost. It is important to remember, that towering up unnecessarily can lose you the game. You win by being offensive, destroying the castle or forcing RS, towers do not contribute to those. Towers also give reduced income, if you're tied on income, blindly spamming towers might make you lose the income battle.
The items
The items can be bought for gold (and sometimes lumber). The effects vary from permanent auras to consumable spells and temporary buffs. Buying items means not spending that cash on permanent buildings and not gaining income and lumber but the effects are sufficiently powerful. Using those items in a correct manner with give huge buffs and possibly force your enemy to RS or lose, using them too much will starve you in income and units. Use them with surgical precision to deliver a killing blow and not waste the effects.