Project Gutenberg is a great resource for free books, but its 50,000+ titles are intimidating in number (if not outright impenetrable). The same goes for other free ebook aggregators/feeds, of which there are many. There are also lots of authors who offer up their books for free. And, of course, there are tons of free options available in, say, the Kindle store. While it's nice to have so many choices, it hinders discoverability. Individual books get lost in all the noise.

As such, I'd like to know: what are some standout, recommended books that are available to readers for free?

Obvious disclaimer: I am not interested in pirated content.

I was reading up on information theory today, and I managed to keep track of everything for a while. But then the information got slippery, and I could feel the muscles in my head tighten. I kept reading, and I lost track of everything. My forehead was so tense I felt it would collapse on itself. By the end of the page, I was exhausted and I closed the book and took a breath. This happens to me every time things get hard. It's like I am lifting weights but I can only do a few reps before I completely crash. If I keep crashing, eventually I'll get a headache that will put me out of commission for the day.

I'm sharing this because I am curious how others feel when they reach their mental limit, either short term or long term. Does anyone else have a similar physical reaction or any physical reaction?

I'd put this series on hold, because of lack of activity. Now I'll give it another go, with French, one of the languages with huge amounts of influential literature.

So, without further ado, please share your favourite French books and authors!

I apologize if this is the wrong topic for this post, and if this feature already exists, I apologize for that too. I looked around and couldn't find it (it's possible I could have missed it). But I thought a dark mode for Tildes would be most excellent. Right now, there's a lot of white space and combined with my 24" monitor, this site lights up my whole room like it's in the middle of the day. Anyways, thanks for reading. :)

~movies.horror?
~life.parenting?
~creative.poetry.limericks?
~comp.dev.games.godot?
~tildes.taxonomy? ;)

The possibilities are, of course, endless. Right now, with few users, we're all still living in top-level land, but I think it would be interesting to see what everyone's more specific interests are, as well as how some people would tackle defining a hierarchy. (e.g. ~games.overwatch vs. ~games.fps.overwatch vs. ~games.multiplayer.fps.overwatch etc.).

Furthermore, what content would you like to see in your specific subgroups? What types of posts would make having them worthwhile?

I've never really been that into video games. When I was young, I played a lot of RPGs on the SNES and PS1. Within the last couple of years, I dipped my toes back in the water and tried a few out. I tried Skyrim on a friend's recommendation, but it was just a little too involved and open-world for me. I got Cities:Skylines, which I love because I love city builder sims, but that game just does not run well on any of my underpowered computers. And I loved Ori and the Blind Forest, a beautiful platformer, and I'd play it again right now if it wasn't Windows-only.

Here are my requirements. First, it needs to run well on a low-powered machine without making the fan go insane. I've got a MacBook Air 2012 and a ThinkPad x250 (Linux). Neither of these are the ideal gaming experience, I know, but I'm not looking for amazing graphics or bleeding edge technology or something super immersive. Pixel graphics are fine with me. It reminds me of my youth, anyway. I played both Skylines and Ori on my Intel NUC 4th Gen and while it worked, they both really taxed that little machine. I was able to finish Ori, but once a city reaches a certain size in Skylines, it gets unplayable.

I'm not looking for stress. I like RPGs and sims. But it doesn't have to be really hard or frustrating. I don't want to feel chased in a game. I prefer to feel that I'm driving the action and I can go at my pace. I want to feel like if I look away for a moment, I'm not going to lose everything. I'm a casual. I also don't mind if there's no defined ending of a game. For me, I'm more looking for a diversion and a slow build over some kind of constant progression/achievement type scenario.

If it has full controller support, that would be ideal. I've got a Steam controller, and I prefer using a controller to play a game. I've never liked using the keyboard to play. I'm not totally against it, but I guess I just never got into computer gaming. I pretty much always played on consoles in the past.

Linux or macOS only, please. I did have Windows installed once so that I could play games, but I'm not bothering with that anymore. I don't want to have to boot into another operating system just to play a game. I want to be able to hop in and out of a game while using my daily driver computer.

So in my research, I've looked into Terraria and Stardew Valley. These might be what I'm looking for. But I really don't know. Do either of these scratch my itch? Is there another game that I would enjoy based on what I've told you? Thanks in advance for any advice you can offer.

EDIT: Thank you everybody for your awesome suggestions. I'm still happy to hear more, as I plan to add the ones that really interest me to my wishlist and revisit later. I ended up getting Hollow Knight yesterday and I spent the whole day playing it. It's very engrossing, and it's the perfect game for me. It's so much like Ori, and that game blew me away. Chilled out, go at your own pace, exploring dungeons, challenging but not impossible (though the first Hornet fight was pretty tough for me). The game runs fine on my ThinkPad x250 (i5-5300U) in Pop!_OS Linux, apart from the initial movie scene stuttering--I just had to skip past it, unfortunately. It's such an awesome game, and I'm glad to see they've already announced a sequel. If you know of any other games that are like Ori and Hollow Knight, let me know.

Introduction

I want to give an introduction on several physics topics at a level understandable to laypeople (high school level physics background). Making physics accessible to laypeople is a much discussed topic at universities. It can be very hard to translate the professional terms into a language understandable by people outside the field. So I will take this opportunity to challenge myself to (hopefully) create an understandable introduction to interesting topics in modern physics. To this end, I will take liberties in explaining things, and not always go for full scientific accuracy, while hopefully still getting the core concepts across. If a more in-depth explanation is wanted, please ask in the comments and I will do my best to answer.

Previous topics

Bookmarkable meta post with links to all previous topics

Today's topic

Today's topic is spintronics storage devices for computers. I will try to explain how we can use an electron's spin to read and write data and why this is more efficient than current technologies.

What do we need to have a storage device?

In order to be able to save a bit (a 0 or a 1 in computer science speak), we need to be able to represent both the 0 and the 1 in some physical way. We could for example flip a light switch and say light on is 1, light off is 0. We will also need to be able to read the information we stored, in this case we can simply look at the lamp to see if we're storing a 0 or a 1. We would also like for this information to be stored even when power is cut, so that next time we power the hardware back on, we will still be able to read the data. Lastly, we want to be able to change between 0 and 1 freely; no one wants to go back to the CD days for storage.

Now for some basic concepts.

What is spin?

Spin arises from quantum mechanics. However, for the purpose of explaining spin storage devices we can think of an electron's spin as a bar magnet. Each electron can be thought of as a freely rotating bar magnet that will align itself with the fields from nearby magnets. Think of it as a compass (the electron) aligning itself to a fridge magnet when it's held near the compass.

Why are some metals magnetic?

Why can we make permanent magnets out of iron, but not copper? In all metals, we have spins that are free to rotate. This means that we can turn a metal into a magnet by holding it near another magnet, it will "copy" the other magnet's magnetisation - its spins will rotate in the direction of the field. But as soon as we remove the magnet, our metal will stop being magnetic. This is because the spins are freely rotating, the spins will align to the magnet's magnetisation when they feel it, but nothing is holding them in place as soon as it's removed. We call this property paramagnetism.

However, iron (and some other metals) will retain a nearby magnet's magnetisation even when the magnet is removed. This is because in these materials, called ferromagnets, it costs energy for the spins to rotate away from the material's magnetisation. They are pinned into place.

What happens if we expose half of our ferromagnet to a magnetisation pointing in one way (let's call it up), and the other half to a magnet whose magnetisation is pointing the other way (which we call down)? The ferromagnet would copy both magnetisation directions and create a boundary region - a so-called domain wall - in the centre. The spins in this domain wall will slowly rotate over the thickness of the wall so that at one end they're pointing up and at the other end they're pointing down.

How can we use spin to store data?

What if, instead of a light bulb, we used a bar magnet as our storage medium. We could magnetise our bar magnet in one direction to store a 1 and magnetise it in the other direction to store a 0. To read what we have stored, we simply check the bar magnet's magnetisation.

Let's work out this idea. We want to be able to efficiently change the magnetisation of a bar magnet and we want to be able to read the bar magnet's magnetisation. We will use a ferromagnet because it will retain our data indefinitely (its magnetisation will not change unless we force it to). We know it costs energy to flip the spins inside a ferromagnet, so we will want to use a very tiny ferromagnet - it will have less spins which means it will cost us less energy to change the magnetisation (i.e. flip the spins).

Magnetoresistance

A-ha, now we're getting into the fancy-titled paragraphs. What do you, dear reader, think would happen when we send a current (e.g. a bunch of electrons) through a magnet? What would happen to the current's electrons (also called itinerant electrons, to distinguish them from the non-moving electrons of the metal)? At the boundary of the magnet, where the current enters, only the electrons who (through random chance) have a spin that's aligned to the magnet's magnetisation will pass through. We call this effect magnetoresistance, as in effect part of our current will feel a resistance - they cannot pass through to the magnet. So to rephrase, the current inside the magnet will be "magnetised" - all of the spins of the itinerant electrons are pointing the same way.

Current induced domain wall motion

So now we know what happens to a current that's inside a magnet. What happens when this current meets a domain wall - the region where the magnetisation changes direction? The itinerant electrons' spins will start rotating along with the magnetisation, but the static electrons of the ferromagnet will also start rotating in the opposite way due to the magnetisation they feel from the current (more experienced readers will recognise this as conservation of angular momentum). So the spins inside the current will slowly rotate until they are pointing the opposite direction and can continue passage from the up-magnetised part of the ferromagnet into the down-magnetised part. But the spins that belong to the ferromagnet itself will be rotating in the opposite manner, slowly rotating from down to up as the current passes through. This means the boundary region between up and down magnetisation, the domain wall, will move along with the current.

So in short, by sending a current through a magnet that's magnetised in opposite directions at each end, we can force our preferred magnetisation to expand in the current's direction. By reversing the direction of the current we can then magnetise the other way again.

So we can say magnetising up (pushing current through (let's say) from left to right) can be our 1 and magnetising down (pushing current through from right to left) can be our 0. This would allow us to store data permanently as even when we remove the current our magnet will remember its magnetisation. If we make a really tiny ferromagnet we will only need a really tiny current to flip it's magnetisation too. So we can scale this process down to get to really good efficiencies. In the lab these types of devices are down to nanometre scale and require extremely little current to be operated.

Reading the data

OK, so now we know how to write data. But how do we read it? The key effect here will be magnetoresistance, as explained earlier in the post.

Let's look at this picture. The red dotted line shows our write currents, the big bar is our ferromagnet. The arrows pointing up and down at the sides are our magnetisation direction, the double-pointed arrow in the centre shows the region where we flip the magnetisation by sending through a current.

Now we jam a third, permanently magnetised, bit of metal (let's call it the read terminal) on top of the centre of our bar. We send a current from this read connector to one of the ends of the ferromagnet. If the ferromagnet's magnetisation is aligned to that of the read terminal we will experience a low (magneto)resistance, but if the ferromagnet is magnetised in the opposite direction we will experience a high resistance. By measuring the difference in resistance we can determine if we have a 0 or a 1 stored. We just need to be careful not to send too big of a current, else that would influence our ferromagnet's magnetisation. But small currents means better efficiency, so this is not a problem at all.

Conclusion

This concludes the post, we have seen how to use spins and magnets to both write and read data and we understand why this is efficient.

Feedback

As usual, please let me know where I missed the mark. Also let me know if things are not clear to you, I will try to explain further in the comments!

Hi,

I've been mulling ideas about a game for a while now, I'd like to hack out a prototype, and my default would be Love2D. (As an aside: one of the things I like about Love2D was that you could make a basic 'game' in a couple of LoC, and it was 'efficient enough' for what you got. Perhaps the only gripe I had with it was that it didn't output compiled binaries (I mean, you could make it do that, but it seemed like a hack). I think Polycode seemed to be a semi-serious contender, but last I checked (a year or two ago) it's pretty much as dead as a doornail. Some of the other alternatives I remember seeing (Godot? Unity?) felt too much like Blender.

So I've been wondering, it's been a while since I've been keeping tabs on the 'gamedev community', so I don't know if there have been any more recent development in that space.

So I guess my question is: What are people using for game jams nowadays? Preach to me (and everyone else) about your favorite framework and language :)

it's time for another one of these threads. the last one racked up an impressive 100 comments in its run, by far the most of any of these threads so far, so that seems like a good sign for this thread. anyways, here you can share/provide updates on some of the projects that you're working on. they can be of any kind--digital, physical, work related, passion project, whatever. pretty straightforward, i think.

november thread • february thread • march thread • april thread • may thread

There doesn't appear to be an app for tildes unless I'm not looking using the right name, how would users here feel about an app similar to what reddit has like reddit is fun or Joey? I'm mainly on my phone and while it's still easy to navigate by browser would love a similarly structured app for tildes. What do you guys think?