     $el.css {background}
     if background
       setTimeout (-> flash $el,''), 50
+  bell = -> flash ($ 'body'), 'black'
 
   matr = rend (Matr
     rows:[]

    #   )
    #   document.title = "Matri"  # XX  debug
    # later {mod, key}

    switch Object.keys(ruh)[0]
      when 'txt' then update rows: [mapr.rows..., ruh.txt]
      when 'tan' then ruh.tan.split("\n").reverse().map (txt)-> peer {txt}
      when 'hop' then update cursor: ruh.hop; bell() # XX buffer.transpose?
      when 'pro' then update prompt: ruh.pro.cad
      when 'blk' then console.log "Stub #{str ruh}"
      when 'det' then buffer.receive ruh.det; sync ruh.det.ted
      when 'act' then switch ruh.act
        when 'clr' then update rows:[]
        when 'bel' then bell()
        when 'nex' then update
          input: ""
          cursor: 0
