srsly guys
beat sans :) what strategies did you guys use for undyne/sans and/or hard mode?
And speaking of hard mode, do you think Toby Fox will ever be coming out with a complete hard mode? What do you think we can expect?
Suggesting that there is a "strategy" to beating Sans makes it seem like there's an easy way out of the boss fight... and if you think that, you're missing the entire point of the fight. This fight was clearly intentionally designed to kill you as many ways possible, and is basically impossible to beat using reactions alone. The game/creator clearly designed it to have you beat the fight by learning Sans' moves, and have it so that is the ONLY way you can beat the fight. Thematically this fits perfectly with what the fight is trying to accomplish; Chara wins the fight though knowing what attacks Sans will use (by abusing infinite timelines, you can essentially "see the future") and through sheer DETERMINATION. The only way you can win the fight is if you, the player, is determined enough to sit through the same fight potentially hundreds of times, as Flowey puts it, just to know what would happen.
It's why the Genocide ending is so hauntingly perfect. The game warns you, begs you, pleads with you throughout the run to stop what you're doing. Then it gives you a nearly impossible fight that only the truly determined will beat. And then it punishes you in the best way possible - temporarily deleting the world, and then tainting every future save. You knew what you were doing. You deserved it.
On a lighter note, Hard mode isn't that hard (as long as it's just the Ruins as it is now, anyway). There's enough healing items and all the save points heal, so if you just play some avoidance around monsters (almost all of them can be spared in 2 turns, if there are multiple fleeing is an option) that it's not that bad. Toriel avoids killing you, so just getting to that fight is the hard part. I'm not sure if this strategy changes if you try to kill the monsters, I did a "pacifist" hard mode run and didn't have much trouble.
Undyne is hard, almost as hard as Sans, but a lot of her attacks are reaction based as opposed to memorization based. It's just another fight that takes time to perfect.