Like so many things in life… practice makes perfect! I only do Code 19s on my tablet because I find I am much better at gauging when the slider will be over the target, some people prefer doing it on their phone. Some players prefer to tap anywhere on the screen… I seem to do better when I am tapping directly on where the slider target is. You mostly just have to learn to watch it moving back and forth and anticipate when it’s going to be on top of the target… without jumping the gun and hitting it too soon (my biggest problem!) There are certain patterns in how they appear as well that regularly doing them will make it easy to recognize and it becomes almost automatic on the timing when to tap.
It helps as well to understand how the Code 19 levels are determined, at least for me, so I know even before it starts when the sliders will be.
First, Code 19 levels are primarily set by the rarity level of the creature. I keep all my common paddocks (other than hybrids) stashed unless I’m really low on coins, as they get very poor rewards… but if you are just learning Code 19s, keep them out so you can have more easier ones to practice on before going up to the harder ones. With rare paddocks, I hatch all the extra copies I get and don’t evolve them right away to make sure they always have at least 11 creatures in the paddock to maximize rewards. As much as possible, I leave creatures at lower levels to fill the paddocks and get better rewards, as long as I don’t really need them for any other game use.
As I get up into the higher rarities, the class of creatures comes into play more. Carnivores have the easiest Code 19s with a max 30 point Code 19… and only 1 slider at the end. So these are my favorites, easy to get perfect scores on. Full Indoraptor paddocks for instance… easy Code 19 with pretty good DNA reward.
Herbivores are the next hardest, also max of 30 points, with 2 sliders, with the first one usually appearing in the second spot, and tends to have patterns that are fairly easy to learn.
And then the amphis and pteros… that’s where you get 3 sliders, which are the most challenging… but of course the highest DNA rewards as well (a perfect score on my Metria paddock is over 1000). So I personally am stashing about 2/3 of those paddocks (particularly with 6 Code 19s to do!) since I so rarely get perfect scores when there’s 3 sliders. I leave out the ones with the highest DNA rewards that are still worthwhile even if not done perfectly (gorgosuchus for instance) but anything that maxes out around 400 or less gets stashed, so I can maximize my chances of getting carnivore or herbivore Code 19s instead. By grouping all my ptero and amphi paddocks near each other and by the repository, and having a specific order to stash them and then put them back in reverse order, it takes only a minute for me to do this… and greatly improving my daily take of DNA as a result. And greatly reducing my annoyance with Code 19s!
If I get to a point where I’m pretty regularly getting all the sliders I might leave more of the 31 point paddocks out, but considering how long I’ve been doing them and still regularly miss on these… stashing those harder paddocks is a strategy that works very well for me. I set a daily alarm on my Amazon Echo to remind me 5 minutes before the Code 19s go active so that I remember to stash the paddocks and also switch over to my tablet so I don’t accidentally have them pop up on my phone.
So hope that helps. Depends on your personal level of interest on doing Code 19s whether this is something to do or not, but at least it will give you some insight into what determines the level that you get.