Why does this keep saying that Mouse is nil?

p = script.Parent
player = game.Players:GetPlayerFromCharacter(p)
Mouse = player:GetMouse()
ls = p.Torso['Left Shoulder']
rs = p.Torso['Right Shoulder']
lh = p.Torso['Left Hip']
rh = p.Torso['Right Hip']
n = p.Torso['Neck']
la = p['Left Arm']
ra = p['Right Arm']
debsphere = false
debfire = false
Mouse.KeyDown:connect(function(Keyf)
    if Keyf == 'f' and not debsphere then
        debsphere = true
        p.Torso.Anchored = true
        ls.C0 = ls.C0 *CFrame.Angles(0,-.4,-1.5)
        rs.C0 = rs.C0 *CFrame.Angles(0,.4,1.5)
        sphere = Instance.new('Part', p)
        sphere.CanCollide = false
        sphere.Transparency = .5
        sphere.Shape = 'Ball'
        sphere.Anchored = true
        sphere.BrickColor = BrickColor.new('Really red')
        sphere.Size = Vector3.new(2,2,2)
        sphere.CFrame = p.Torso.CFrame *CFrame.new(0,0,-2)
        wait(.5)
        ls.C0 = ls.C0 *CFrame.Angles(-.42,.04,1.5)
        rs.C0 = rs.C0 *CFrame.Angles(-.42,-.04,-1.5)
        p.Torso.Anchored = false
		sphere.Touched:connect(function(hit) print(hit)
			hit = sphere:FindFirstChild('Humanoid')
			if hit~= nil then
				player:WaitForDataReady()
				hit.Health = Health -20
				demlvlexp = player:LoadNumber('demlvlexp')
				demlvlexp = demlvlexp +5
				player:SaveNumber('demlvlexp', demlvlexp)
				if hit.Health == 0 then
					demlvlexp = player:LoadNumber('demlvlexp')
					demlvlexp = demlvlexp +25
					player:SaveNumber('demlvlexp', demlvlexp)
				end
			end
		end)
		function move()
			for moving = 1, 75 do
				wait(.01)
				sphere.CFrame = sphere.CFrame *CFrame.new(0,0,-.4)
			end
			for goaway = 1, 10 do
				wait(.01)
				sphere.Transparency = sphere.Transparency +(.05)
				sphere.CFrame = sphere.CFrame *CFrame.new(0,0,-.4)
			end
			sphere:remove()
		end
		move()
		wait(10)
        debsphere = false
    end
end)
Mouse.KeyDown:connect(function(Keyg)
	if Keyg == 'g' and not debfire then
		player:WaitForDataReady()
		if player:LoadNumber('demlvl') >= 7 then
		debfire = true
		p.Torso.Anchored = true
        ls.C0 = ls.C0 *CFrame.Angles(0,-.4,-1.5)
        rs.C0 = rs.C0 *CFrame.Angles(0,.4,1.5)
        fsphere = Instance.new('Part', p)
        fsphere.CanCollide = false
        fsphere.Transparency = .5
        fsphere.Shape = 'Ball'
        fsphere.Anchored = true
        fsphere.BrickColor = BrickColor.new('Really red')
        fsphere.Size = Vector3.new(2,2,2)
        fsphere.CFrame = p.Torso.CFrame *CFrame.new(0,0,-2)
        wait(.5)
        ls.C0 = ls.C0 *CFrame.Angles(-.42,.04,1.5)
        rs.C0 = rs.C0 *CFrame.Angles(-.42,-.04,-1.5)
        p.Torso.Anchored = false
		fsphere.Touched:connect(function(hit) print(hit)
			hit = fsphere:FindFirstChild('Humanoid')
			if hit~= nil then
				player:WaitForDataReady()
				hit.Health = Health -20
				demlvlexp = player:LoadNumber('demlvlexp')
				demlvlexp = demlvlexp +5
				player:SaveNumber('demlvlexp', demlvlexp)
				if hit.Health == 0 then
					demlvlexp = player:LoadNumber('demlvlexp')
					demlvlexp = demlvlexp +25
					player:SaveNumber('demlvlexp', demlvlexp)
				end
			end
		end)
		function move()
			for moving = 1, 75 do
				wait(.01)
				fsphere.CFrame = fsphere.CFrame *CFrame.new(0,0,-.4)
			end
			for goaway = 1, 10 do
				wait(.01)
				fsphere.Transparency = fsphere.Transparency +(.05)
				fsphere.CFrame = fsphere.CFrame *CFrame.new(0,0,-.4)
			end
			fsphere:remove()
		end
		move()
		wait(10)
		debfire = false
		else
		end
	end
end)

that should work.. it works in studio but not in play

Are you using a LocalScript? GetMouse only works from LocalScripts (unless you are in PlaySolo, which would explain your trouble)