How can I make a CSGO style "Buy Menu" inventory?

What I'm trying to make is an inventory similar to the CSGO "Buy Menu" or the inventory from SCP Secret Laboratory. Here's what it looks like.

https://gyazo.com/bf11da81dc16f9199eb93320712299b8

What I want to accomplish is when the mouse hovers over a certain section the lit up part lights up that section. I cant make buttons that match the shape of the selection so I cant light up an area when its hovered over. Any ideas on how to make this happen?

Use MouseHoverEnter function.

Example:

script.Parent.MouseEnter:Connect(function()
	script.Parent.BackgroundTransparency = 1
end)

script.Parent.MouseLeave:Connect(function()
	script.Parent.BackgroundTransparency = 0
end)

When the mouse enters the button, it will change the transparency to 1, when it leaves, it changes it to 0.