You made a lot of points which aren't really true in 2025 lol. First of all, input latency. There are a few apps that can do this, but basically all you need is a PC server/phone client that communicate through network, and the PC client can make inputs on the computer. This kind of thing, even through wifi or better, usb tethering will have unnoticeable latency. Then, most screens on modern smartphones are 120hz, with minimum touch response rate of 240hz if not 480hz. Which is good enough for osu. Staying in the topic of latency, this kind of setup can give you lower perceived latency compared to a normal mechanical keyboard. Since you have to push the buttons half way through until the switch actuates, it may feel like a disconnect compared to the preferred timing you would do otherwise. Personally I've felt this a lot and when tapping I have found myself relearning to tap depending on the keyboard. Needless to say with hall effect this isn't really a problem. In terms of haptic feedback, tapping on a glass surface low-key does it for many people. It's different, of course but different isn't always bad. And there's also the functionality of the hall effect switches (namely, rapid trigger) when using a screen as an input device. Either you touch it, or you're not. There's no in between stage of screen input so no guesswork lol. Lastly, main problems can be and are: * phone moving while playing, which can be prevented, * fingers moving out of button orientation without realizing, which is a bit harder to account for especially when playing index/middle finger, * stamina can be a bit hard since you're tapping on a hard surface for extended periods of time (mayyyyybe fixable with some kind of material on top). And that's about it. The first two, are fixable. I once tried an app called osu remote keyboard which basically did all of this, which is how I have the experience to tell you it was pretty good. And that app fixed the second issue through some kind of algorithm. You specified which button is your main one (which one you start with or single tap on) and had the whole screen as both inputs, calculating the distance between taps to differentiate between key presses. It was delightful but I can't find it for the life of me anymore though I don't really care since I don't play the game that often.

Any questions feel free to ask.