10 ms·

Show HN: I built an autopilot for the lunar lander game

277 points by szhu 4y ago

I got pretty good at (and very addicted to) the lunar lander game from a few days ago... so I decided to make an autopilot for the lander based on what I felt like was the best strategy! Now I can have perfect landings every time without lifting a finger :D Writing the autopilot code was a lot more fun than I expected! It felt a bit like programming a robot. Source code: https://github.com/szhu/lunar-lander-autopilot https://github.com/szhu/lunar-lander-autopilot Original lander HN post: https://news.ycombinator.com/item?id=35032506 https://news.ycombinator.com/item?id=35032506

monkellipse 4y ago
Nice! I also got hooked on the lander thing, really quick to pick up and good replay value! Your autopilot handles a gentle landing well. If I get the lander going sideways at any appreciable speed, then flip autopilot on, a crash is inevitable :) As a human my solution to that is simply slowing down with lots of thrust, though I still wind up turning the lander into scrap most of the time hah!
huevosabio 4y ago
Love it! I started playing by disabling autopilot, putting the ship in complicated positions (e.g. spinning uncontrollably) and then turning the autopilot on, it's fun to which conditions it can recover.
000ooo000 4y ago
Cool, neat code too :) Now do https://race-condition.reaktor.com/ https://race-condition.reaktor.com/! I wanted to pour a few hours into race condition but I got it to complete a lap and never went back.
tiffanyh 4y ago
Mobile? How to you trigger autopilot on mobile?
- skipnup 4y ago
  Click on the red glowing "autopilot" link to turn on on (glowing green)
mg 4y ago
It's interesting to think about how the optimal strategy to land the lander would look like. If the distance to the moon was large, I would expect 4 phases: 1: Turn the lander towards the moon 2: Constant thrust towards the moon 3: Turn the lander away from the moon 4: Constant thrust away from the moon But if the initial distance is small enough, turning it around might not be worth it or even possible. So the optimal strategy is probably a somewhat complex function of the initial angle and distance to the moon.
- swyx 4y ago
  almost guaranteed that this problem is already solved by the rocket scientists out there. hopefully someone on HN can point us to the relevant algorithm. this seems like a closed system at least in newtonian physics that should be easily solvable. chatgpt pointed me to the Gravity Turn altho it refused to give me a formula for it https://en.wikipedia.org/wiki/Gravity_turn#Deorbit_and_entry https://en.wikipedia.org/wiki/Gravity_turn#Deorbit_and_entry
  - antoinealb 4y ago
    This is typically solved using a class of control algorithm called Model Predictive Control which are capable of optimizing for a given cost function (such as using minimal fuel). Search for "fuel optimal rocket landing algorithm" for good starting points.
- 4gotunameagain 4y ago
  when discussing about optimality, it is worth specifying what are you optimising for. time optimal landing lends techniques from bang-bang control (e.g. starting with v=0, max thrust towards the target, before flipping around half way and max thrust away from target) fuel optimal landing (incuding RCS) technique would depend on the available time to turn retrograde (pointy end pointing away from direction of movement). if the duration before the decelerating burn is T1 (so t1 = t0+T1), the smallest possible rcs impulse would be applied so that at t1-T_st the lander is pointing retrograde (retrograde at t1), with T_st being the time needed to cancel the initial rcs impulse. For the deceleration of the lander, fuel optimal landing includes a single burn, constantly retrograde, so that at t_end the lander altitude is 0, and both the vertical and horizontal velocity components are 0. The time t1 to start that burn depends on the maximum thrust available, the rate of mass change when firing the rocket (not modelled in the game), the initial velocity etc. in this simple case, model predictive control is not needed, and an LQR (linear quadratic regulator) is sufficient to achieve optimality source: rocket scientist with control theory background. I remember this example (a bit more realistically modelled) being a project during my studies
timmaxw 4y ago
I wanted to go for a record of as many flips as possible. So I boosted up to 25,000 feet; started spinning until it was doing about one flip per second; waited a few minutes; then turned on the autopilot to come into a landing. The autopilot did a perfect job of stopping the rotation and lateral motion, so the lander came down straight as an arrow. Unfortunately, the autopilot didn't even try to decelerate! I crashed into the moon at 0.9 degrees and 770 MPH.
- ricardobeat 4y ago
  The target velocity is a factor of height, and the autopilot has “160” hardcoded as the ceiling, so going above that means it will never decelerate fast enough. https://github.com/szhu/lunar-lander-autopilot/blob/master/autopilot.js#L67 https://github.com/szhu/lunar-lander-autopilot/blob/master/a...
  - szhu 4y ago
    That's a ceiling for the speed the autopilot is okay with letting the lander descend. There is no ceiling to how much hard it will try to "apply the brakes". I agree that the target velocity calculation is off though. I was excited that I came up with something reasonably theoretically correct for correcting rotation... and for figuring out when to fire the engines I just gave up and eyeballed it :)
- szhu 4y ago
  Update: I added a new algorithm, and I think it might be impossible to crash the ship now. Let me know if you can still reproduce the bug!
  - manbash 4y ago
    Max speed: 148.7 Max height: 3998 Flips: 34 Perfect landing. :)
  - timmaxw 4y ago
    Yep, it lands safely now!
dropbox_miner 4y ago
This is great but I'd like to see an autopilot that can do the hardest crash
josephcsible 4y ago
One suggestion: if the lander is within about 10 feet of the ground and is still either swaying back and forth or going really fast laterally, it should thrust upwards to buy more time to correct those things.
- szhu 4y ago
  oh yeah definitely. Left as an exercise for the reader?? (accepting PRs!)
  - szhu 4y ago
    Actually, I think my new algorithm fixes this -- and without any dedicated "swaying" edge case!
deleted 4y ago
[deleted]
marketdev 4y ago
While I was playing the game, the idea of traveling in a SpaceX rocket ship didn't seem appealing to me. Now that I have experienced your autopilot feature, I feel MUCH more confident about it.
ricardobeat 4y ago
It’s amazing how a simple algorithm performs so well, the autopilot is able to recover from some pretty extreme situations, and does it gracefully. Adding some realism to the engine physics (firing delays, minimum firing time, power ramp up, heat limits etc) would likely make it 10x harder.
- giomasce 4y ago
  Especially nondeterminism. Everything you say is still deterministic, so either you're able to land or you're not. With nondeterminism it's more interesting. You have to make tradeoffs between optimizing resources and making success probable.
- dwringer 4y ago
  Thanks for this comment, I hadn't thought to try and sabotage my trajectory prior to engaging autopilot. I thought for sure it was gonna fail, but it managed to set me down gently right at the last moment quite brilliantly.
hawski 4y ago
Would it be possible to put the autopilot in a bookmarklet for the original game?
- szhu 4y ago
  I really wanted to! But unfortunately none of the lander's stats are exposed as global variables, so the only way I could make the autopilot was by modifying the existing code. (My commits are actually broken down exactly like this: a commit to expose the necessary variables globally, and another to actually add the autopilot.) I would also love to be able to play it in the original game though, so I made a PR! I think it would be cool for it to be able to be activated as an easter egg. https://github.com/ehmorris/lunar-lander/pull/7 https://github.com/ehmorris/lunar-lander/pull/7
  - ehmorris 4y ago
    I will take a look!
curiousgal 4y ago
Best I could score was 102.0 with a combination of manual and autopilot. Neat!
handonam 4y ago
this is great! The one thing i think to optimize it is to predict how late to start the engine to minimize its usage. The last I got was 730 times used, at 53seconds.
- dsmmcken 4y ago
  choosing how late you can turn it on and still land is almost a game in itself.
tommica 4y ago
What about adding a limited fuel supply?
- acomjean 4y ago
  For what it’s worth fuel is in the original arcade game. “Unlike other arcade games, Lunar Lander does not feature a time limit; instead, the game starts with a set amount of fuel and inserting additional quarters purchases more fuel, allowing indefinite gameplay.“ https://en.m.wikipedia.org/wiki/Lunar_Lander_(1979_video_game) https://en.m.wikipedia.org/wiki/Lunar_Lander_(1979_video_gam...
simonh 4y ago
That's cool, but it has a very conservative descent profile and would use a ton of fuel. Having played Kerbal I'm used to attempting fuel efficient landings, which means more of a suicide burn approach, but of course this game doesn't keep track of that. There's something timelessly appealing about lunar lander games. The very first game I ever played on a computer, written in BASIC, was a 'turn based' one dimensional lunar lander game where you input how much thrust you used for each second of the descent, and then it recalculated your altitude, velocity, etc. I learned programming by rewriting it to be a real-time game where you pressed a key to fire the engine.
- mft_ 4y ago
  Which points to a lovely idea - the game becomes writing competitive lander algorithms. Just need a bit of JSFiddle adding...
  - santiagobasulto 4y ago
    That'd be very fun indeed!
    - someweirdperson 4y ago
      Maybe not for long, because for a given set of constraints to optimze for, there's probably a solution for which it can be proven to be optimal. At that point there's no more contest.
      - rizky05 4y ago
        [dead]
      - TheMaskedCoder 4y ago
        Obviously next you switch up the game to do things besides lunar landing. Have it be a take off ascent simulator for example. After a few years we can have an entire space mission programmed by gamers...
deleted 4y ago
[deleted]
m00dy 4y ago
very similar to https://www.gymlibrary.dev/environments/box2d/lunar_lander/ https://www.gymlibrary.dev/environments/box2d/lunar_lander/
- szhu 4y ago
  Oh yeah, the author of the game said he made use of a similar tutorial: http://students.cs.ucl.ac.uk/schoolslab/projects/HT5/ http://students.cs.ucl.ac.uk/schoolslab/projects/HT5/ from the readme here: https://github.com/ehmorris/lunar-lander https://github.com/ehmorris/lunar-lander
_ZeD_ 4y ago
uhm... it doesn't seem to work, at least on my workstation (firefox on a debian)
- szhu 4y ago
  oh no! I'm tried it on Firefox on Mac and it worked fine? https://user-images.githubusercontent.com/1570168/224370129-6f80c7b1-1626-4b6f-900e-611b06f3a4a9.png https://user-images.githubusercontent.com/1570168/224370129-... https://user-images.githubusercontent.com/1570168/224369935-56894894-4f7d-41a2-87de-830cc9c4ae06.mov https://user-images.githubusercontent.com/1570168/224369935-...
ehmorris 4y ago
Woah this is awesome! Someone on Twitter made an autopilot with ML but this seems a lot better. https://twitter.com/_s_w_a_y_a_m_/status/1633468475611004928?s=20 https://twitter.com/_s_w_a_y_a_m_/status/1633468475611004928...
Nodraak 4y ago
Nice auto pilot! Very basic, but works well enough. In the real world, you would derive physics equations (acceleration -> velocity -> position), add constraints and then solve everything to obtain an optimal trajectory (mostly in term of fuel, but you can add other constraints too, for ex due to radar-ground or Antenna-Earth visibility). I wrote a blog post about Apollo's algorithm: https://blog.nodraak.fr/2020/12/aerospace-sim-2-guidance-law/ https://blog.nodraak.fr/2020/12/aerospace-sim-2-guidance-law... (Described in the second section ; the first section is about a naive algorithm similar to yours that in the end did not work as well as I wanted). Also, thanks for the code, I wanted to do the same, but lost motivation when I could not really expose in a satisfying way the internal state out of these JS modules (it's not complicated in the end, but I'm simply not a frontend dev ; and I wanted to avoid forking and monkey patching everything and simply adding some JS code throught the console or something).
paradite 4y ago
Lunar lander is a one of the problems in Open AI Gym, where you test AI against standard set of problems: https://www.gymlibrary.dev/environments/box2d/lunar_lander/ https://www.gymlibrary.dev/environments/box2d/lunar_lander/ Then you have stable baselines which implements popular reinforcement learning algorithms to solve these gym problems: https://stable-baselines3.readthedocs.io/en/master/ https://stable-baselines3.readthedocs.io/en/master/ Shamless plug: I've built a series of games where you solve puzzles (2048) / toy problems (MDP) like the lunar lander using various AI and ML algorithms. You can check it out here: https://ai-simulator.com/ https://ai-simulator.com/
- hcrisp 4y ago
  Yes, I would like to see the environment ported to Python, wrapped in gym, and given a good shaped reward, i.e. like reward = prior_height_delta - (height - target_height) - fuel_cost. Run Stable Baselines PPO or DQN on that and it should converge to something close to an optimized MPC controller.
  - paradite 4y ago
    It is already there, just not this particular implementation (or maybe it is?). You can run PPO or DQN right now on the Open AI Gym implementation using Stable-Baselines3: https://stable-baselines3.readthedocs.io/en/master/ https://stable-baselines3.readthedocs.io/en/master/ In fact I previously ran it locally and PPO solved the problem within 10 minutes of training with max reward of about 200.
    - hcrisp 4y ago
      This is a different lunar lander than you are maybe thinking. It looks more like SpaceX's Starship than an Apollo lunar module. I don't think it has been made into a gym env yet but that would be great if it is!
- opdahl 4y ago
  Looking at your website I’m curious how exactly you’re building «ChatGPT for mobile games»? Are you using language models to build these AI solvers?
kevinwang 4y ago
And now we've gone full circle
- mclightning 4y ago
  That was my immediate thought. 1.Step: Write code to simulate freefall of an object 2.Step: Write code to negate freefall of an object
antegamisou 4y ago
Now do it with LQR :D
bjd2385 4y ago
Really cool! The fact that astronauts handled the landing in the Apollo missions is nerve wracking
Aperocky 4y ago
A career in KSP is calling for you (Landing on the mun automatically): https://www.youtube.com/watch?v=TY63i8V1-DA https://www.youtube.com/watch?v=TY63i8V1-DA The most I've used linear algebra since college: https://github.com/Aperocky/ksp_eng/blob/master/lib/space_lib.ks#L301 https://github.com/Aperocky/ksp_eng/blob/master/lib/space_li...
iandanforth 4y ago
I'm impressed by the simplicity of the solution, well done.
- szhu 4y ago
  Thanks! Yeah it's just (1) rotate to follow the trajectory line and (2) slow down once you get close to the bottom.
jkonline 4y ago
"Oh SNAP! I'm amazing at this!" 101.1 point landing on my second try! At least, that's what I thought, until I realized I had previously activated the auto-pilot. Best #footgun today (so far!). So I guess I should say: > Oh SNAP! This auto-pilot is amazing at this! Thanks!
tired_and_awake 4y ago
Simple and fun, thanks for sharing! Have you thought of adding a wordle style variation - just a daily puzzle that's a different start orientation + velocity? Just a thought.
- szhu 4y ago
  Oh that sounds like fun, I would definitely play that. You should suggest it to the developer who made the game! https://github.com/ehmorris/lunar-lander/issues https://github.com/ehmorris/lunar-lander/issues https://news.ycombinator.com/item?id=35032506 https://news.ycombinator.com/item?id=35032506
szhu 4y ago
Update: I improved the algorithm. The autopilot now scores a "perfect landing" almost every single time, it lands very noticeably faster, and the code no longer contains a complicated, trial-by-error formula! I got my first 103+ point landing! (It does this about half the time now) https://user-images.githubusercontent.com/1570168/224399420-5a8d688a-9306-4499-aea0-5e9e212b438e.png https://user-images.githubusercontent.com/1570168/224399420-...
khalidx 4y ago
This is awesome! The closest I got without the autopilot was 94 or so. The autopilot consistently scores 100+
mckirk 4y ago
I can confirm that with the improved auto-pilot it is possible to get a 103.6 point landing after performing 1,151 flips (and reaching a max speed of 504 mph and a height of about 38k feet), if you can spare your phone for 38 minutes.
- szhu 4y ago
  I admire your dedication! Thank you for sacrificing 38 minutes of screen time for a noble cause.

277 points by szhu 4y ago

monkellipse 4y ago

Nice! I also got hooked on the lander thing, really quick to pick up and good replay value! Your autopilot handles a gentle landing well. If I get the lander going sideways at any appreciable speed, then flip autopilot on, a crash is inevitable :) As a human my solution to that is simply slowing down with lots of thrust, though I still wind up turning the lander into scrap most of the time hah!

huevosabio 4y ago

Love it! I started playing by disabling autopilot, putting the ship in complicated positions (e.g. spinning uncontrollably) and then turning the autopilot on, it's fun to which conditions it can recover.

000ooo000 4y ago

Cool, neat code too :) Now do https://race-condition.reaktor.com/ https://race-condition.reaktor.com/! I wanted to pour a few hours into race condition but I got it to complete a lap and never went back.

tiffanyh 4y ago

Mobile? How to you trigger autopilot on mobile?

skipnup 4y ago
Click on the red glowing "autopilot" link to turn on on (glowing green)

mg 4y ago

It's interesting to think about how the optimal strategy to land the lander would look like. If the distance to the moon was large, I would expect 4 phases: 1: Turn the lander towards the moon 2: Constant thrust towards the moon 3: Turn the lander away from the moon 4: Constant thrust away from the moon But if the initial distance is small enough, turning it around might not be worth it or even possible. So the optimal strategy is probably a somewhat complex function of the initial angle and distance to the moon.

swyx 4y ago
almost guaranteed that this problem is already solved by the rocket scientists out there. hopefully someone on HN can point us to the relevant algorithm. this seems like a closed system at least in newtonian physics that should be easily solvable. chatgpt pointed me to the Gravity Turn altho it refused to give me a formula for it https://en.wikipedia.org/wiki/Gravity_turn#Deorbit_and_entry https://en.wikipedia.org/wiki/Gravity_turn#Deorbit_and_entry
- antoinealb 4y ago
  This is typically solved using a class of control algorithm called Model Predictive Control which are capable of optimizing for a given cost function (such as using minimal fuel). Search for "fuel optimal rocket landing algorithm" for good starting points.
4gotunameagain 4y ago
when discussing about optimality, it is worth specifying what are you optimising for. time optimal landing lends techniques from bang-bang control (e.g. starting with v=0, max thrust towards the target, before flipping around half way and max thrust away from target) fuel optimal landing (incuding RCS) technique would depend on the available time to turn retrograde (pointy end pointing away from direction of movement). if the duration before the decelerating burn is T1 (so t1 = t0+T1), the smallest possible rcs impulse would be applied so that at t1-T_st the lander is pointing retrograde (retrograde at t1), with T_st being the time needed to cancel the initial rcs impulse. For the deceleration of the lander, fuel optimal landing includes a single burn, constantly retrograde, so that at t_end the lander altitude is 0, and both the vertical and horizontal velocity components are 0. The time t1 to start that burn depends on the maximum thrust available, the rate of mass change when firing the rocket (not modelled in the game), the initial velocity etc. in this simple case, model predictive control is not needed, and an LQR (linear quadratic regulator) is sufficient to achieve optimality source: rocket scientist with control theory background. I remember this example (a bit more realistically modelled) being a project during my studies

timmaxw 4y ago

I wanted to go for a record of as many flips as possible. So I boosted up to 25,000 feet; started spinning until it was doing about one flip per second; waited a few minutes; then turned on the autopilot to come into a landing. The autopilot did a perfect job of stopping the rotation and lateral motion, so the lander came down straight as an arrow. Unfortunately, the autopilot didn't even try to decelerate! I crashed into the moon at 0.9 degrees and 770 MPH.

ricardobeat 4y ago
The target velocity is a factor of height, and the autopilot has “160” hardcoded as the ceiling, so going above that means it will never decelerate fast enough. https://github.com/szhu/lunar-lander-autopilot/blob/master/autopilot.js#L67 https://github.com/szhu/lunar-lander-autopilot/blob/master/a...
- szhu 4y ago
  That's a ceiling for the speed the autopilot is okay with letting the lander descend. There is no ceiling to how much hard it will try to "apply the brakes". I agree that the target velocity calculation is off though. I was excited that I came up with something reasonably theoretically correct for correcting rotation... and for figuring out when to fire the engines I just gave up and eyeballed it :)
szhu 4y ago
Update: I added a new algorithm, and I think it might be impossible to crash the ship now. Let me know if you can still reproduce the bug!
- manbash 4y ago
  Max speed: 148.7 Max height: 3998 Flips: 34 Perfect landing. :)
- timmaxw 4y ago
  Yep, it lands safely now!

dropbox_miner 4y ago

This is great but I'd like to see an autopilot that can do the hardest crash

josephcsible 4y ago

One suggestion: if the lander is within about 10 feet of the ground and is still either swaying back and forth or going really fast laterally, it should thrust upwards to buy more time to correct those things.

szhu 4y ago
oh yeah definitely. Left as an exercise for the reader?? (accepting PRs!)
- szhu 4y ago
  Actually, I think my new algorithm fixes this -- and without any dedicated "swaying" edge case!

deleted 4y ago

[deleted]

marketdev 4y ago

While I was playing the game, the idea of traveling in a SpaceX rocket ship didn't seem appealing to me. Now that I have experienced your autopilot feature, I feel MUCH more confident about it.

ricardobeat 4y ago

It’s amazing how a simple algorithm performs so well, the autopilot is able to recover from some pretty extreme situations, and does it gracefully. Adding some realism to the engine physics (firing delays, minimum firing time, power ramp up, heat limits etc) would likely make it 10x harder.

giomasce 4y ago
Especially nondeterminism. Everything you say is still deterministic, so either you're able to land or you're not. With nondeterminism it's more interesting. You have to make tradeoffs between optimizing resources and making success probable.
dwringer 4y ago
Thanks for this comment, I hadn't thought to try and sabotage my trajectory prior to engaging autopilot. I thought for sure it was gonna fail, but it managed to set me down gently right at the last moment quite brilliantly.

hawski 4y ago

Would it be possible to put the autopilot in a bookmarklet for the original game?

szhu 4y ago
I really wanted to! But unfortunately none of the lander's stats are exposed as global variables, so the only way I could make the autopilot was by modifying the existing code. (My commits are actually broken down exactly like this: a commit to expose the necessary variables globally, and another to actually add the autopilot.) I would also love to be able to play it in the original game though, so I made a PR! I think it would be cool for it to be able to be activated as an easter egg. https://github.com/ehmorris/lunar-lander/pull/7 https://github.com/ehmorris/lunar-lander/pull/7
- ehmorris 4y ago
  I will take a look!

curiousgal 4y ago

Best I could score was 102.0 with a combination of manual and autopilot. Neat!

handonam 4y ago

this is great! The one thing i think to optimize it is to predict how late to start the engine to minimize its usage. The last I got was 730 times used, at 53seconds.

dsmmcken 4y ago
choosing how late you can turn it on and still land is almost a game in itself.

tommica 4y ago

What about adding a limited fuel supply?

acomjean 4y ago
For what it’s worth fuel is in the original arcade game. “Unlike other arcade games, Lunar Lander does not feature a time limit; instead, the game starts with a set amount of fuel and inserting additional quarters purchases more fuel, allowing indefinite gameplay.“ https://en.m.wikipedia.org/wiki/Lunar_Lander_(1979_video_game) https://en.m.wikipedia.org/wiki/Lunar_Lander_(1979_video_gam...

simonh 4y ago

That's cool, but it has a very conservative descent profile and would use a ton of fuel. Having played Kerbal I'm used to attempting fuel efficient landings, which means more of a suicide burn approach, but of course this game doesn't keep track of that. There's something timelessly appealing about lunar lander games. The very first game I ever played on a computer, written in BASIC, was a 'turn based' one dimensional lunar lander game where you input how much thrust you used for each second of the descent, and then it recalculated your altitude, velocity, etc. I learned programming by rewriting it to be a real-time game where you pressed a key to fire the engine.

mft_ 4y ago
Which points to a lovely idea - the game becomes writing competitive lander algorithms. Just need a bit of JSFiddle adding...
- santiagobasulto 4y ago
  That'd be very fun indeed!
  - someweirdperson 4y ago
    Maybe not for long, because for a given set of constraints to optimze for, there's probably a solution for which it can be proven to be optimal. At that point there's no more contest.
    - rizky05 4y ago
      [dead]
    - TheMaskedCoder 4y ago
      Obviously next you switch up the game to do things besides lunar landing. Have it be a take off ascent simulator for example. After a few years we can have an entire space mission programmed by gamers...

deleted 4y ago

[deleted]

m00dy 4y ago

very similar to https://www.gymlibrary.dev/environments/box2d/lunar_lander/ https://www.gymlibrary.dev/environments/box2d/lunar_lander/

szhu 4y ago
Oh yeah, the author of the game said he made use of a similar tutorial: http://students.cs.ucl.ac.uk/schoolslab/projects/HT5/ http://students.cs.ucl.ac.uk/schoolslab/projects/HT5/ from the readme here: https://github.com/ehmorris/lunar-lander https://github.com/ehmorris/lunar-lander

_ZeD_ 4y ago

uhm... it doesn't seem to work, at least on my workstation (firefox on a debian)

szhu 4y ago
oh no! I'm tried it on Firefox on Mac and it worked fine? https://user-images.githubusercontent.com/1570168/224370129-6f80c7b1-1626-4b6f-900e-611b06f3a4a9.png https://user-images.githubusercontent.com/1570168/224370129-... https://user-images.githubusercontent.com/1570168/224369935-56894894-4f7d-41a2-87de-830cc9c4ae06.mov https://user-images.githubusercontent.com/1570168/224369935-...

ehmorris 4y ago

Woah this is awesome! Someone on Twitter made an autopilot with ML but this seems a lot better. https://twitter.com/_s_w_a_y_a_m_/status/1633468475611004928?s=20 https://twitter.com/_s_w_a_y_a_m_/status/1633468475611004928...

Nodraak 4y ago

Nice auto pilot! Very basic, but works well enough. In the real world, you would derive physics equations (acceleration -> velocity -> position), add constraints and then solve everything to obtain an optimal trajectory (mostly in term of fuel, but you can add other constraints too, for ex due to radar-ground or Antenna-Earth visibility). I wrote a blog post about Apollo's algorithm: https://blog.nodraak.fr/2020/12/aerospace-sim-2-guidance-law/ https://blog.nodraak.fr/2020/12/aerospace-sim-2-guidance-law... (Described in the second section ; the first section is about a naive algorithm similar to yours that in the end did not work as well as I wanted). Also, thanks for the code, I wanted to do the same, but lost motivation when I could not really expose in a satisfying way the internal state out of these JS modules (it's not complicated in the end, but I'm simply not a frontend dev ; and I wanted to avoid forking and monkey patching everything and simply adding some JS code throught the console or something).

paradite 4y ago

Lunar lander is a one of the problems in Open AI Gym, where you test AI against standard set of problems: https://www.gymlibrary.dev/environments/box2d/lunar_lander/ https://www.gymlibrary.dev/environments/box2d/lunar_lander/ Then you have stable baselines which implements popular reinforcement learning algorithms to solve these gym problems: https://stable-baselines3.readthedocs.io/en/master/ https://stable-baselines3.readthedocs.io/en/master/ Shamless plug: I've built a series of games where you solve puzzles (2048) / toy problems (MDP) like the lunar lander using various AI and ML algorithms. You can check it out here: https://ai-simulator.com/ https://ai-simulator.com/

hcrisp 4y ago
Yes, I would like to see the environment ported to Python, wrapped in gym, and given a good shaped reward, i.e. like reward = prior_height_delta - (height - target_height) - fuel_cost. Run Stable Baselines PPO or DQN on that and it should converge to something close to an optimized MPC controller.
- paradite 4y ago
  It is already there, just not this particular implementation (or maybe it is?). You can run PPO or DQN right now on the Open AI Gym implementation using Stable-Baselines3: https://stable-baselines3.readthedocs.io/en/master/ https://stable-baselines3.readthedocs.io/en/master/ In fact I previously ran it locally and PPO solved the problem within 10 minutes of training with max reward of about 200.
  - hcrisp 4y ago
    This is a different lunar lander than you are maybe thinking. It looks more like SpaceX's Starship than an Apollo lunar module. I don't think it has been made into a gym env yet but that would be great if it is!
opdahl 4y ago
Looking at your website I’m curious how exactly you’re building «ChatGPT for mobile games»? Are you using language models to build these AI solvers?

kevinwang 4y ago

And now we've gone full circle

mclightning 4y ago
That was my immediate thought. 1.Step: Write code to simulate freefall of an object 2.Step: Write code to negate freefall of an object

antegamisou 4y ago

Now do it with LQR :D

bjd2385 4y ago

Really cool! The fact that astronauts handled the landing in the Apollo missions is nerve wracking

Aperocky 4y ago

A career in KSP is calling for you (Landing on the mun automatically): https://www.youtube.com/watch?v=TY63i8V1-DA https://www.youtube.com/watch?v=TY63i8V1-DA The most I've used linear algebra since college: https://github.com/Aperocky/ksp_eng/blob/master/lib/space_lib.ks#L301 https://github.com/Aperocky/ksp_eng/blob/master/lib/space_li...

iandanforth 4y ago

I'm impressed by the simplicity of the solution, well done.

szhu 4y ago
Thanks! Yeah it's just (1) rotate to follow the trajectory line and (2) slow down once you get close to the bottom.

jkonline 4y ago

"Oh SNAP! I'm amazing at this!" 101.1 point landing on my second try! At least, that's what I thought, until I realized I had previously activated the auto-pilot. Best #footgun today (so far!). So I guess I should say: > Oh SNAP! This auto-pilot is amazing at this! Thanks!

tired_and_awake 4y ago

Simple and fun, thanks for sharing! Have you thought of adding a wordle style variation - just a daily puzzle that's a different start orientation + velocity? Just a thought.

szhu 4y ago
Oh that sounds like fun, I would definitely play that. You should suggest it to the developer who made the game! https://github.com/ehmorris/lunar-lander/issues https://github.com/ehmorris/lunar-lander/issues https://news.ycombinator.com/item?id=35032506 https://news.ycombinator.com/item?id=35032506

szhu 4y ago

Update: I improved the algorithm. The autopilot now scores a "perfect landing" almost every single time, it lands very noticeably faster, and the code no longer contains a complicated, trial-by-error formula! I got my first 103+ point landing! (It does this about half the time now) https://user-images.githubusercontent.com/1570168/224399420-5a8d688a-9306-4499-aea0-5e9e212b438e.png https://user-images.githubusercontent.com/1570168/224399420-...

khalidx 4y ago

This is awesome! The closest I got without the autopilot was 94 or so. The autopilot consistently scores 100+

mckirk 4y ago

I can confirm that with the improved auto-pilot it is possible to get a 103.6 point landing after performing 1,151 flips (and reaching a max speed of 504 mph and a height of about 38k feet), if you can spare your phone for 38 minutes.

szhu 4y ago
I admire your dedication! Thank you for sacrificing 38 minutes of screen time for a noble cause.