--by Rylvns
--edited 5/9/26

--!optimize 2
--!native

local FLY_KEY = Enum.KeyCode.LeftShift;
local FLY_UP_KEY = Enum.KeyCode.Space;
local FLY_DOWN_KEY = Enum.KeyCode.LeftControl;

local FLY_SPEED = 50;
local MAX_FLY_SPEED = 400;
local SPEED_INCREMENT = 1;

local COLLISION_RADIUS = 60;

local UserInputService = game:GetService("UserInputService");
local RunService = game:GetService("RunService");
local Players = game:GetService("Players");
local Player = Players.LocalPlayer;

local Character = Player.Character or Player.CharacterAdded:Wait();
local Humanoid = Character:WaitForChild("Humanoid");
local RootPart = Character:WaitForChild("HumanoidRootPart");

local Flying = false;
local FlySpeed = FLY_SPEED;
local OriginalGravity = workspace.Gravity;
local ChangedParts = {};

local OverlapParams = OverlapParams.new();
OverlapParams.FilterType = Enum.RaycastFilterType.Exclude;
OverlapParams.FilterDescendantsInstances = {Character};

local function RestoreAllCollisions()
	for Part in pairs(ChangedParts) do
		if not Part then continue end;
		if not Part.Parent then continue end;
		Part.CanCollide = true;
	end;
	ChangedParts = {};
end;

local function StopFlying()
	Flying = false;
	FlySpeed = FLY_SPEED;
	if RootPart and RootPart.Parent then
		RootPart.AssemblyLinearVelocity = Vector3.zero;
	end;
	workspace.Gravity = OriginalGravity;
	RestoreAllCollisions();
end;

Player.CharacterAdded:Connect(function(NewCharacter)
	if Flying then StopFlying() end;
	Character = NewCharacter;
	Humanoid = Character:WaitForChild("Humanoid");
	RootPart = Character:WaitForChild("HumanoidRootPart");
	OverlapParams.FilterDescendantsInstances = {Character};
end);

RunService.RenderStepped:Connect(function()
	if not Flying or not RootPart or not RootPart.Parent then return end;

	local MoveDirection = Vector3.zero;
	local CameraCFrame = workspace.CurrentCamera.CFrame;
	MoveDirection += UserInputService:IsKeyDown(Enum.KeyCode.W) and CameraCFrame.LookVector or Vector3.zero;
	MoveDirection -= UserInputService:IsKeyDown(Enum.KeyCode.S) and CameraCFrame.LookVector or Vector3.zero;
	MoveDirection -= UserInputService:IsKeyDown(Enum.KeyCode.A) and CameraCFrame.RightVector or Vector3.zero;
	MoveDirection += UserInputService:IsKeyDown(Enum.KeyCode.D) and CameraCFrame.RightVector or Vector3.zero;
	MoveDirection += UserInputService:IsKeyDown(FLY_UP_KEY) and Vector3.yAxis or Vector3.zero;
	MoveDirection -= UserInputService:IsKeyDown(FLY_DOWN_KEY) and Vector3.yAxis or Vector3.zero;

	if MoveDirection.Magnitude > 0 then
		FlySpeed = math.min(FlySpeed+SPEED_INCREMENT, MAX_FLY_SPEED);
		MoveDirection = MoveDirection.Unit*FlySpeed;
		RootPart.AssemblyLinearVelocity = MoveDirection*0.5;
	else
		RootPart.AssemblyLinearVelocity = Vector3.zero;
	end;

	local NearbySet = {};
	for _, Part in ipairs(workspace:GetPartBoundsInRadius(RootPart.Position, COLLISION_RADIUS, OverlapParams)) do
		NearbySet[Part] = true;
		if not Part.CanCollide then continue end;
		if ChangedParts[Part] then continue end;
		ChangedParts[Part] = true;
		Part.CanCollide = false;
	end;

	for Part in pairs(ChangedParts) do
		if NearbySet[Part] then continue end;
		if Part and Part.Parent then
			Part.CanCollide = true;
		end;
		ChangedParts[Part] = nil;
	end;
end);

UserInputService.InputBegan:Connect(function(InputObject, GameProcessedEvent)
	if GameProcessedEvent then return end;
	if InputObject.KeyCode ~= FLY_KEY then return end;
	Flying = not Flying;
	if Flying then
		workspace.Gravity = 0;
	else
		StopFlying();
	end;
end);