After building a column of command blocks that looks like the one in my video, paste the following commands starting from the bottom command block and going up.
The bottom command block is set on "repeat", "unconditional" and "always active". All the others are set on "chain", "unconditional" and "always active".
/execute @e[type=snowball] ~ ~ ~ fill ~ ~ ~ ~ ~ ~ fire 0 replace air
/execute @e[type=snowball] ~ ~ ~ detect ~ ~ ~ fire -1 scoreboard players tag @e[type=snowball,c=1] add GROUND
/execute @e[type=snowball,tag=GROUND] ~ ~ ~ summon creeper ~ ~ ~ {ExplosionRadius:0,Fuse:0}
/execute @e[type=snowball,tag=GROUND] ~ ~ ~ fill ~ ~ ~ ~ ~ ~ air 0 replace fire
/kill @e[type=snowball,tag=GROUND]
Command blocks
Tutorial viewed times
DETECT ANY ENTITY ON THE GROUND