A sun umbrella? -- Such a deal at only $2,500,000,000,000!

I think this is not such a stupid idea although it has a few problems.
I also support the idea of a sun shield in space near L1 and initially
thought of using simple clouds of small reflective discs.

The problems with these is that :-

1) They will slowly drift out of position and can not be controlled
just topped up

2) They may pose a danger to other space craft.

3) They are an inefficient use of material considering how many tonnes
of them are required.

I propose that an alternative is larger controlled shields with a
plasma drive.
Each shield could be a kilometer or more in diameter made of spinning
discs of reflective mylar.