sp {attack*propose*move
   (state <s> ^name attack
              ^io.input-link <input>)
   (<input> ^blocked.<dir> yes
            ^radar <r>)
   (<r> ^tank <t>
       -^tank.position center)
   (<t> ^position { << left right >> <dir> }
        ^distance <> 0)
   -->
   (<s> ^operator <o> + =)
   (<o> ^name move
        ^actions.move.direction forward)}
