Dweets awesomed by u/Xor

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: #Opposites

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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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KilledByAPixel

remix of d/16391 by u/KilledByAPixel

function u(t) {

for(i=340;--i;x.fillRect(960+S(m*m)*q,540+C(m*m)*q,50,50))m=i+120*t,q=1e5/i,x.fillStyle=R(i*i/99,i*i/340)

Oct 31 2019 6:28 AM UTC

}// 105/140

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Supernova ☀

u/katkip

i would like to see this on the sky
u/tomxor

wow!
u/yonatan

and so short!
u/lowtolerance

I don’t understand it at all but I love it

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aemkei

remix of d/7285 by u/aemkei

function u(t) {

x.font="3em'"
x.fillText("ᴀscii",C=0,40)
d=x.getImageData(t*3,Y=t*120%82,2,D=3).data
for(;D<19;)C+=!d[D+=4]
x.fillText("Xw=^ "[C],t*54,Y*22)

Jun 21 2018 8:47 PM UTC

}// 140/140

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#ascii #art Now with 4 symbols.

u/aemkei

5 symbols: x.font="3em'";x.fillText("ᴀscii",C=0,40);for(d=x.getImageData(t*3,Y=t*120%82,2,D=3).data;D<23;)C+=!d[D+=4];x.fillText("Xwo=^ "[C],t*54,Y*22)
u/magna

ASCI version: d/8698
u/magna

3 chars shorter, using existing character set for shading: d/8699
u/aemkei

128 bytes: x.fillText(a=x.font="3em' ",C=0,40);for(d=x.getImageData(t*3,Y=t*120%82,2,D=3).data;D<19;)C+=!d[D+=4];x.fillText(a[C],t*54,Y*22)
u/katkip

#text

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Xen

remix of d/8508 by u/firegodjr

function u(t) {

c.width=333
for(x.shadowBlur=i=30;i--;x.fillRect(155-i*6+S(i*t)*i/9,i*C(i-t*9),i*13,i*9))x.shadowColor='#'+frame

Jun 9 2018 3:21 PM UTC

}// 112/140

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Forbidden-Stairway2: Wrath of Hue

u/pythech

so dope
u/lionleaf

Awesome! #tunnel #stairs #color

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aemkei

remix of d/5293 by u/Xen

function u(t) {

for(c.width|=i=h=999;i--;)x.fillRect(h+h*(2e5-(i-500)**2)**.5/h*S(t+i),i,9,9)

Jan 3 2018 9:50 PM UTC

}// 77/140

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u/iverjo

Wow, only 77 characters
u/iverjo

#sphere

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magna

remix of d/1480 by u/magna

function u(t) {

c.width|=0
x.font='50px monospace';
(u+'')
.slice(0,t*3+S(t)*5)
.concat(t*2&1?'|':'')
.split('\n')
.forEach((s,i)=>x.fillText(s,0,++i*50))

Apr 18 2017 1:55 AM UTC

}// 138/140

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Pair programming nightmare

Show more comments…
u/joeytwiddle

that title made me Lol :D
u/sigveseb

:D
u/Jenky

That's a really clever illusion, love it
u/magna

Heh, thanks! Brought it down to 123 chars in hopes of adding occasional mistakes like skipped characters / typos etc., but couldn't immediately find a way. In case anyone wants to give it a shot: https://www.dwitter.net/d/2522
u/donbright

:o
u/Polyducks

Could you make a random function to skip odd spaces?
u/magna

It has to be a deterministic PRNG so that the places that are skipped are persistent. Otherwise, it would just look like a random flipping of characters. I thought about it, but couldn't immediately find a short solution.
u/Polyducks

That's a great point. Dwitter is such a mind twister!
u/highfestiva

Groovy baby!
u/magna

#quine
u/joeytwiddle

#funny

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