Undefined property on $prop

my code : code
error: image
expected : change in class and remove of the green line from the side

all the involved vue files are merged into one file in my code link ( excluded css )

You have mixed props and data, try remove props: tasks

    props:{
        tasks:Array
    },

and

data(){
    return{
      tasks:[
        {id:1,text:"some title text1",day:"1/1/21",reminder:false},
        {id:2,text:"some title text2",day:"1/1/22",reminder:true},
        {id:3,text:"some title text3",day:"1/1/23",reminder:false},
        {id:4,text:"some title text4",day:"1/1/24",reminder:true},
      ]
    }
  },