Dweets awesomed by u/ManualDoCodigo

function u(t) {

c.width=1920 // clear the canvas
for(i=0;i<9;i++)
x.fillRect(400+i*100+S(t)*300,400,50,200) // draw 50x200 rects

} // 122/140

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    u(t) is called 60 times per second.
    t: Elapsed time in seconds.
    S: Shorthand for Math.sin.
    C: Shorthand for Math.cos.
    T: Shorthand for Math.tan.
    R: Function that generates rgba-strings, usage ex.: R(255, 255, 255, 0.5)
    c: A 1920x1080 canvas.
    x: A 2D context for that canvas.

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Current theme challenge: #Food

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pavel

function u(t) {

for(f=c=>Math.tanh((r>1?3:13)*S(9*c/d)),Y=t/3-1,i=2e3;i--;x.fillRect(i,t*180,(1+f(X)*f(Y))*(d/2+Y/3.6),3))X=i/540-16/9,r=X*X+Y*Y,d=r>1||C(r)

Apr 22 2020 6:18 AM UTC

}// 140/140

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Experimenting with #raytracing. I finally figured out why the cosine trick from d/1112 works.

u/Cloud

WOW!

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cantelope

function u(t) {

for(x[g='fillStyle']='#0003',x[f='fillRect'](0,0,w=i=1920,i);i--;x[f](b%w,(b/w|0)%1080,9,9))x[g]=`hsl(${b=(i+w+t/99)**2.3} 99%50%`

Apr 20 2020 7:04 AM UTC

}// 130/140

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no Math.random

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rodrigo.siqueira

remix of d/18323 by u/pavel

function u(t) {

for(let i=2e3,f=(x,y,n=256)=>x*y<n?f(x*x-y*y-.6,2*x*y+.5,n-1):1-n/256;i--;x.fillRect(i,t*180,1,3))x.fillStyle=R(f(i/490-2,1-t/3)*i,0,i/14)

Apr 18 2020 6:34 PM UTC

}// 138/140

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Color #julia set for c = -0.6 + 0.5i #fractal

u/sigveseb

Nice colors

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pavel

remix of d/18322 by u/pavel

function u(t) {

for(let i=1920,f=(x,y,n=256)=>x*y<n?f(x*x-y*y-.8,2*x*y+.156,n-1):1-n/256;i--;x.fillRect(i,t*180,1,3))x.globalAlpha=f(i/540-16/9,1-t/3)

Apr 18 2020 8:32 AM UTC

}// 134/140

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#julia set for c = −0.8 + 0.156i

Show more comments…
u/pavel

Using x*y<n instead of the normal n&&x*x+y*y<2 is much shorter and creates the black whisps that look pretty cool.
u/pavel

This version makes it easy to play with different values of c. You can find some in https://en.wikipedia.org/wiki/Julia_set#Quad…
u/pavel

https://en.wikipedia.org/wiki/Julia_set#Quad…
u/pavel

Is link pasting broken?
u/Xen

Sexy!
u/katkip

wow
u/katkip

https://en.wikipedia.org/wiki/Julia_set
u/rodrigo.siqueira

Awesome and fast. I am remixing it to add color schemes and colorization methods.
u/Qwitter

SO FAST!

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pavel

remix of d/13495 by u/pavel

function u(t) {

for(i=t?c.width|=C=_=>u[j=q+n&-n|p/n]=-!u[j]|1:p=q=r=s=571;i--;u[i]||x.fillRect(i?i%n*n:p+=r*=C(p+=r),i?i&-n:q+=s*=C(q+=s),z=i?n:15,-z))n=64

Apr 11 2020 10:31 PM UTC

}// 140/140

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#breakout

Show more comments…
u/pavel

Fixed the tilted look, the missing upper left block, and increased the size of the ball.
u/pavel

Why does changing 571 break the code for most values? :)
u/pavel

472, 582, 593 work well though
u/iznax

The code seems to work with most starting values if you change it to "C=_=>(p|q)<0?-1:u[j=q+n&-n|p/n]=-!u[j]|1" and handle negative coordinates as blockers?
u/KilledByAPixel

👍
u/pavel

Its shorter to init positions and velocities to same number but makes velocities too fast. Another problem is that init needs to happen once and shortest way to do that is t?<spot>:init which creates a spot to do something every non-first frame. I solve both problems by naming my collision detection function C and defining it on every non-first frame. On the first frame C is Math.cos so the velocity update code does r = r*C(p+=r) = 571*Math.cos(571+571) = 17.7 which is a reasonable speed.
u/pavel

The ball needs to be updated once per frame. Since I am iterating with a single index its easiest to check for index 0. This corresponds to the upper left block which is why it was missing in the original. A short fix is to shift everything up one block by using negative height for the blocks and adding a row to ball position encoding. The +n in q+n&-n|p/n.
u/pavel

I encode and decode 2d co-ordinates into one number. The block coordinates are (i%n,i/n|0) and their width is n making their real positions (i%n*n,(i/n|0)*n). Lets simplify the second one. If we choose n=2**k then (i/n|0)*n = (i/2**k|0)*2**k = (i>>k)<<k so we are zeroing out the last k binary digits. But if n=2**k then -n is a bunch of ones followed by k zeroes (https://en.wikipedia.org/wiki/Two%27s_comple…)! Therefore (i/n|0)*n = i&-n.
u/pavel

Need to check if ball pos (p,q) touches a new block. Ball is always in some block, find that blocks pos index. Dividing ball position by n gives the virtual coords and blocks are 1x1 so truncating gives 2d block coordinates (p/n|0,q/n|0). Want to encode this into index j where (x,y)=(j%n,j/n|0). Therefore j=(q/n|0)*n+(p/n|0). If n=2**k then in binary j=[32-k binary digits y-coord][k binary digits of x-coord] so we can use bitwise-or which also auto-truncates so j=(q/n|0)*n|p/n. And as we saw (q/n|0)*n=q&-n so j=q&-n|p/n! Real code uses j=q+n&-n|p/n to add one row to ball pos to account for shift up to hide missing (0,0)` block.
u/pavel

p+=r*=C(p+=r) encodes an unbelievable trick that is perfect for collision detection. For detection we need to independently try advancing vertically and horizontally, check for collision, and reverse course if hit. The temporary state involved in trying can cost a lot of chars. p+=r*=C(p+=r) does it all and C doesn't even read its argument! When C is invoked the global p it sees was already incremented by r. However, the outer p+= will eventually discard that increment. Magic!
u/rep_movsd

Un-effing-believable
u/hvianna

Wow, this is insane!
u/jylikangas

Masterclass in code golfing!
u/13thptr

awesome, looks like the ball escapes without breaking everything after a while though. will read the explanation more thoroughly.
u/pavel

No chars left for bounds checks! It freaks out with negative positions. If I find a way to shorten I will add bounds.
u/ersagun

I need to read and reread that explanation on a loop until I get this. This is incredible.
u/Qwitter

Just wow.

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rodrigo.siqueira

remix of d/17953 by u/tomxor

function u(t) {

c.width=-1;for(i=2e3;m=i&1,v=(K=t%2)<1?25:K%1*99**1.1,p=i%3*3,i--;)x.fillRect(150+p*S(P=i**.7)+v*C(V=i**.5+t),78+p*C(P)+v*S(V)*C(!p*i),1,1)

Mar 16 2020 11:30 AM UTC

}// 139/140

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Blowing The Enemy #coronavirus

Show more comments…
u/WorldMerge

This is really cool! Does setting the canvas width to -1 make it full-width?
u/rodrigo.siqueira

c.width=-1 is a trick I saw here (probably from u/pavel) that makes width=300 pixels. I used throw(c.width) to see "300". So it's a compact form to create a medium-low resolution image.
u/tomxor

300px is the default canvas width. What's particularly odd is that while setting negative numbers causes default value, everything else that ordinarily coerces to NaN will result in 0. e.g throw Number({}).toString() // NaN c.width={}; throw c.width.toString() // 0
u/tomxor

I guess in c++ land width has outofrange=300 and NaN=0
u/katkip

looks good
u/katkip

but dangerous

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