watcher=klass()
function watcher:init(ruleset,seed,stages)
 self.ruleset=ruleset
 self.seed=seed
 self._stages=stages or {}
end
function watcher:active_stage(board)
 local stage=self._stages[1]
 if (stage and stage:active()) return stage
end
function watcher:intercept(x,arg)
 local stage=self:active_stage()
 if (not stage) return true
 local allowed,drop=stage:intercept(x,arg)
 if (drop) deli(self._stages,1)
 return allowed
end
function watcher:draw(board)
 local stage=self:active_stage()
 if (not stage) return

 local layouts=board.ruleset.layouts
 local layout,i,x,y,text
 layout,i,text=stage:draw(board,layouts)

 x,y=layout:place_card(i)
 local w,h=measure_text(text)
 x+=1
 y+=20
 local lx=x+3
 line(lx,y-4,lx,y,15)
 rectfill(x-2,y-2,x+w,y+h,1)
 rect(x-2,y-2,x+w,y+h,15)
 print(text,x,y,15)
end

tutorial_grab=klass()
function tutorial_grab:init(src,dst)
 self.src=src
 self.dst=dst
end

function tutorial_grab:active()
 return true
end

function tutorial_grab:intercept(x, slot)
 if (x=="grab" and slot==self.src) return true,false
 if (x=="drop" and slot==self.dst) return true,true
end
function tutorial_grab:draw(board,layouts)
 local layout,i,text
 if board.cursor:acceptance_state() == acceptance_state.not_grabbed then
  -- show a hint for grabbing
  layout=layouts:slot(self.src)
  i=#board.slots[self.src].contents
  draw_layout_hint(layout,i,15,false,0,0)
  text="🅾️"
 else
  layout=layouts:slot(self.dst)
  i=#board.slots[self.dst].contents+1
  draw_layout_hint(layout,i,15,false,0,0)
  text="🅾️"
 end
 return layout,i,text
end


tutorial_undo=klass()
function tutorial_undo:init() end
function tutorial_undo:active()
 return true
end
function tutorial_undo:intercept(x)
 if (x=="undo") return true,true
end
function tutorial_undo:draw(board,layouts)
 local layout,i,text
 layout=layouts:checkpoint()
 draw_layout_hint(layout,0,15,false,0,0)
 text="❎"
 return layout,i,text
end

-- todo: restart?