I'm currently creating a custom 8 direction movement with acceleration and deceleration.
It's all working fine, except for a weird annoyance. Moving diagonally works most of the time, but on some occasions when pressing two keys at once and letting them go after half a second it will still think that one of the keys is being pressed. It's almost like there is a small amount of input detection lag.
It does the same thing if I use the basic Clickteam 8 direction movement.
I thought it might be my keyboard, but I tested it in The Binding of Isaac Rebirth (has 8 direction movement as well) and there is no issue with this weird input lag and the player continues in the diagonal direction no matter how short the key press combinations are..
Let me know if it's doing the same thing for you in the example below. To get it doing weird things, press either left and up, left and down or right and up or right and down pretty rapidly. You should notice that the deceleration continues diagonally most of the time, but on occasions, will straighten out to a cardinal direction.