// Lighting the furnace is cosmetic for now, but burns a log.
pub fn toggle(ctx) {
    if ctx.variant() == "lit" {
        ctx.set_variant("");
        ctx.message("You let the furnace cool down.");
        return;
    }
    if !ctx.take_item("log", 1) {
        ctx.message("You need a log to light the furnace.");
        return false;
    }
    ctx.set_variant("lit");
    ctx.message("The furnace roars to life.");
}