/summon minecraft:armor_stand ~ ~-0.24 ~ {Small:1b,Invisible:1b,NoGravity:1b,CustomName:"Half",Passengers:[{id:"falling_block",TileID:1,Data:0,Time:1,CustomName:"Half",NoGravity:1b},{id:"shulker",NoAI:1b,CustomName:"Half",NoGravity:1b,Silent:1b,Invulnerable:1b}]}

Summons an armor stand with a shulker and a falling block in it. If you want to change the block, change the TileID value with the id of your block, and the Data with the data value of your block (Press f3+h to know ids and datas). If you want to change the position of the block, just change its coordinates

/effect @e[type=shulker,name=Half] 14 1 1 true

Makes the shulker invisible, by giving it an invisibility effect

/entitydata @e[type=falling_block,name=Half] {Time:1}

Prevents the falling block from despairing, so the block can stand where you placed it forever

/scoreboard objectives add time dummy

Adds a score called "dummy": this score will be used to change the highscore

/scoreboard objectives add highscore dummy

Adds a score called "highscore": this one will be changed with the scoreboard command

/scoreboard players operation @a highscore > @a time

This command changes "highscore"'s value in "time"'s value, but only if "time"'s value is higher than "highscore"'s value: if you want the score to change when "time"'s value is lower, just replace the ">" with "<"

/scoreboard players add @a time 1

This command adds 1 to the score

/scoreboard players set @a time 0

This score is used to reset the score. If you want to reset the hgscore, just replace "time" with "highscore"

/execute @e[type=endermite,name=Meteor] ~ ~ ~ summon arrow ~ 255 ~ {CustomName:"meteor"}

An endermite called Meteor summons an arrow at highness 255

/kill @e[type=endermite,name=Meteor]

Kills teh undermine, so it doesn't summon any other arrow

/execute @e[type=arrow,name=meteor] ~ ~ ~ summon tnt ~0.1 ~1 ~0.1

The arrow summons some tnt nearby it (The x/z coords are the meteorite's inclination, the y coord is its speed)

/execute @e[type=arrow,name=meteor] ~ ~ ~ detect ~ ~-1 ~ bedrock 0 kill @e[type=arrow,name=meteor,r=0]

When the arrow is on bedrock, it kills itself

/scoreboard objectives add meteor dummy

/execute @e[type=endermite,name=Meteor] ~ ~ ~ summon arrow ~ 5 ~ {CustomName:"meteor"}

/kill @e[type=endermite,name=Meteor]

/execute @e[type=arrow,name=meteor] ~ ~ ~ summon tnt ~0.1 ~-2 ~0.1

/scoreboard players add @e[type=arrow,name=meteor] meteor 1

/kill @e[type=arrow,name=meteor,score_meteor_min=100]