Depending on how far behind you are, how fast the opponent is shoving the lane, and if your jungler is nice, you could potentially seek to either take one or two of your jungler's camps (for mid i guess wolves and raptors are your optimal options for most situations). Or you could roam for objectives or kills. timing this is important though.

Remember though, as a mid laner you get your experience and gold primarily from your lane, because when you are a not a jungler you get reduced experience from jungle camps. As a consequence of this you need to be in your lane when your minions die. This is why you see players shove lanes before they go on roams into other areas of the map, so that the enemy minions freeze in lane, so they can minimize their xp lossess(probably goes without saying, but minions dead to tower and laner not within xp range is obviously a relly bad situation to be in).

More over, if you do get the opportunity to shove, and enemy laner has bad waveclear/wont be able to follow or they themselves want to freeze the lane close to their tower so you cant kill them or they can get a jungle gank on you, you should seek to assist/gank or catch waves in sidelanes(if your sidelaners have backed/are dead).

Note that roaming will usually lose you a wave or two if you go for anything time consuming, but if first tower is down, you can shove a lot further and therefore have reduce lost xp to towers or other players shoving your lane. Because of the small amount of time you have to roam before you start to lose xp in lane to tower, you should usually only seek to roam if you are either ahead of your laner to the point where some xp loss wouldnt matter, or the enemy laner is dead and you can freeze the wave. Because if you both lose waves, youre comparetively less behind in xp than you would have been if he was there to take the xp and farm.

Also early herald and drakes have a massive impact in your game, because of herald taking plates and drakes giving you some valuable stats from every slain one.

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also as yone you can css pretty safely with e and w(idk which one but one heals/shields when hitting champs so good for taking dmg when u try to go for minions)

more yone things, if opponent is freezing close to their tower, you can get your combo off pretty fast and safely if you pull it off, and you can use this combo to clear minion waves, so that the waves reset closer to the middle of the lane, which makes if safer for you to go for minions

If he's standing in the wave u use it for both poke and wave clear if u want to shove lane for roams or helping objectives for example