Help Minecraft 1.14 pre-release 5 commands

Question

First, I'm a noob to the command community. Also, this is what I'm making for a survival series I call Atlantis. I got bored of Minecraft so this is what I'm doing for a solution. The command in theory is supposed to slow me down whenever I touch air.

So the command I am trying is the following:

/execute if block ~ ~2 ~ Minecraft:air as @a run effect give @a Minecraft:slowness 999999 20 true

This does not work. Any ideas?

Edit: Does it matter if it is conditional or unconditional. Same question for command block type.

Answer 1

You have several errors at once.

1)You run a block check from the artist and not from all players.

2)Many commands are case sensitive.

3)You are testing 2 blocks at the top.

That will be correct:

/execute as @a at @s if block ~ ~-0.51 ~ minecraft:air run effect give @s minecraft:slowness 999999 20 true

Note: In order for the check to work not from the executor of the command, but from the players over which the check takes place, we add "at @s" after "as @a".