Macro style_signal 

style_signal!() { /* proc-macro */ }

Reactive style macro that supports Leptos signals in CSS values

Usage:

let (count, _) = create_signal(cx, 0);
let class = style_signal! {
    .counter {
        font-size: #{(count() * 2 + 16)}px;
        color: #{if count() > 10 { "red" } else { "blue" }};
    }
};

The macro parses CSS with embedded Rust expressions in #{...} blocks, extracts signal dependencies, and generates reactive update code.