Offscreen indicator for sprites

Hello!

I was wondering if something like this would be possible for sprites.
I'm working on a setup that involves several shells moving around, and some of them go offscreen for a few seconds, and it would be much better for the player if they could tell where the shells are at all times.

A UberASM or a placeable sprite solution would be preferable, so it doesn't apply to other levels/setups.

Thank you!

I also thought about this idea in the past - would be very useful for all those shells that drop offscreen for the player to catch to make a shelljump or to know a "danger" is hidden there but also to prevent some blind jumps on sprites etc.

I'll try this out

Completed here.

sorry, took me a while to tag this as claimed

And thank you,  Kevin!!!