# Show me some fireworks!

Given, in any way and order,

• dimensions (in whichever order you want)

• a probability (in whatever format you want)

• number of iterations (you may choose whether to count the initial state or not)

do one of the following:

• animate, or

• output each step of, or

• return a list of states of

a spaces-filled sky of those dimensions.

For each iteration:

• every sky character has the given probability of becoming a *

• the eight characters that surround any * become
\ | /
-      -
/ | \, if they don't become stars, however,

• if a character is within range of two *s, make it an X

### Example

The 7×22 sky (frame for clarity only – don't output the frame)

┌──────────────────────┐
│                      │
│                      │
│                      │
│                      │
│                      │
│                      │
│                      │
└──────────────────────┘


could with 1% probability become

┌──────────────────────┐
│  *                   │
│                      │
│                      │
│                      │
│                      │
│           *          │
│                      │
└──────────────────────┘


and the next step

┌──────────────────────┐
│ - - *                │
│ /|\                  │
│          *           │
│                      │
│          \|/         │
│          - -         │
│          /|\         │
└──────────────────────┘


and then

┌──────────────────────┐
│    - -               │
│    /|\  \|/          │
│         - -          │
│         /|\          │
│                      │
│      * *             │
│                      │
└──────────────────────┘


and

┌──────────────────────┐
│                      │
│                      │
│                      │
│                      │
│     \|X|/            │
│     - X -            │
│     /|X|\          * │
└──────────────────────┘


and so on

┌──────────────────────┐
│                      │
│                      │
│                      │
│                   *  │
│                      │
│                   \|/│
│                   - -│
└──────────────────────┘

• If someone viewing this is not familiar at all about the USA culture, they might be confused to why you are launching fireworks on 4th July.
– Okx
Jul 4, 2017 at 17:56
• @Okx to destroy all who oppose, of course! Jul 17, 2017 at 21:29
• Obligatory xkcd Jul 19, 2017 at 14:22

# ES6, 520 496 bytes

Clipping and everything else should work now.

(w,h,p,i,r=0,s=($=>{while(++r<i)for(j=0,_=$[r]=[],z=$[r-1]||[];j<w*h;){k=j+1,l='*',c=0 n=(j%w&&z[j-1]==l&&++c)|(k%w&&z[k]==l&&++c)?'-':' ' n=(z[j-w]==l&&++c)|(z[j+w]==l&&++c)?'|':n n=(j%w&&z[j-w-1]==l&&++c)|(k%w&&z[k+w]==l&&++c)?'\\':n n=(k%w&&z[k-w]==l&&++c)|(j%w&&z[j+w-1]==l&&++c)?'/':n _[j++]=Math.random()<p?l:c>1?'X':n}})(x=[])||x)=>{c=document.body.children[0],r=0;while(++r<i)setTimeout((k=0)=>{for(r++,c.innerHTML='';k<h;)c.innerHTML+=s[r].slice(k*w,++k*w).join('')+'\n'},90*r);r=0}  View animation! Saved 24 bytes thanks to Zacharý's tip. ## Old solution, 478 bytes (with clipping bug) I think I got all the rules correct, however the solution has a clipping problem where everything exiting right/left wraps around one line lower/higher on the opposite side. (w,h,p,i,r=0,s=($=>{while(++r<i)for(j=0,_=$[r]=[],z=$[r-1]||[];j<w*h;){c=0
n=(z[j-1]=='*'&&++c)|(z[j+1]=='*'&&++c)?'-':' '
n=(z[j-w]=='*'&&++c)|(z[j+w]=='*'&&++c)?'|':n
n=(z[j-w-1]=='*'&&++c)|(z[j+w+1]=='*'&&++c)?'\\':n
n=(z[j-w+1]=='*'&&++c)|(z[j+w-1]=='*'&&++c)?'/':n
_[j++]=Math.random()<p?'*':c>1?'X':n}})(x=[])||x)=>{c=document.body.children[0],r=0;while(++r<i)setTimeout((k=0)=>{for(r++,c.innerHTML='';k<h;)c.innerHTML+=s[r].slice(k*w,++k*w).join('')+'\n'},90*r);r=0}


View old.

• Nicely done. Can't you fix the clipping by appending blank columns on the sides, animate, and then chop?
Jul 4, 2017 at 21:24
• Couldn't you define a variable to be '*' since you use it SO often? Jul 5, 2017 at 21:28
• @Zacharý Good tip, I will define variables for '*' and other commonly used things. Jul 5, 2017 at 22:07
• If only JS had macros. Jul 5, 2017 at 22:35

# APL (Dyalog), 65 chars or 71 bytes*

Prompts for dimensions (rows, columns), then for iterations (not counting initial state), then for probability (as n in ¹⁄).

⎕{1=?⍺⍺:'*'⋄2≤+/b←'*'=1↓4⌽,⍵:'X'⋄⊃b/'-/|\\|/-'}⌺3 3{⍺⍺⎕←⍵}⍣⎕⊢⎕⍴''


Try it online!

⎕⍴'' prompt for input and use that to reshape an empty string, padding with spaces as needed

⊢ yield that

⍣⎕ prompt for input and apply the following function on the above () that many times:

…{} derive a function using the below function as operand (⍺⍺), as follows:

⎕←⍵ print the argument

⍺⍺ apply the following function:

…⌺3 3 apply the following function on each element's 3×3 Moore neighborhood:

⎕{} get input and use it as operand (⍺⍺) to derive a new function

?⍺⍺ random integer among the first ⍺⍺ integers

1= Boolean if equal to one

: if true:

'*' return a star

⋄ else:

,⍵ ravel (flatten) the argument (the Moore neighborhood)

4⌽ rotate it cyclically four steps to the left

1↓ drop one element (the original center)

'*'= Boolean list where equal to a star

b← store that as b

+/ sum that

2≤ Boolean if two or higher

: if true:

'X' return an X

⋄ else:

b/'-/|\\|/-' use the b to to filter the string

⊃ pick the first one, if there are none, pick the prototype (a space)

* To run in Dyalog Classic, simply replace ⌺ with ⎕U233A .