Вот скрипт;
local Mos = game.Players.LocalPlayer:GetMouse()

--Если нажата
Mos.KeyDown:connect(function(key)
if key:lower() == string.char(48) then
game.Workspace.Camera.FieldOfView = game.Workspace.Camera.FieldOfView + 1.6
local Player1 = game.Players.LocalPlayer.Character.Humanoid
if Player1 then
Player1.WalkSpeed = 25
end
end
end)

--Если отпущена
Mos.KeyUp:connect(function(key)
if key:lower() == string.char(48) then --Если нажата
game.Workspace.Camera.FieldOfView = game.Workspace.Camera.FieldOfView - 1.6
local Player1 = game.Players.LocalPlayer.Character.Humanoid
if Player1 then
Player1.WalkSpeed = 16
end
end
end)

свернуть