｛｝
 The title of this article is incorrect because of technical limitations. The correct title is {}.
{} is a family of esolangs by User:PythonshellDebugwindow.
Level 1
{} Level 1 was the first attempt at an esolang in the {} family, although it was horribly ambiguous, too much so to parse (for human and machine alike). It uses an unbounded signed integer accumulator called acc.
Commands
Command  Meaning 

{} 
0 
{{x}} 
While acc > 0 do x (x can be any number of commands > 0) 
{x} 
Set acc to x 
{x{y} 
x + y 
{{}} 
acc 
A {}
as x inside a {x}
is indistinguishable from a {{}}
.
Computational class
Due to its ambiguity, Level 1 is uncomputable.
Level 2
{} Level 2 was the second attempt at an esolang in the {} family. Like Level 1, it was too ambiguous to program in, and it uses an unbounded signed integer accumulator called acc.
Commands
Command  Meaning 

{} 
0 
{x} 
acc = x (also evaluate to x) 
{xy} 
If x then do y (y can be any number of commands > 0) 
{{xy}} 
While x ≠ 0 do y (y can be any number of commands > 0) 
{{}} 
acc 
{{x}} 
acc + x + 1 
Computational class
Like Level 1, Level 2 is uncomputable due to its excessive ambiguity.
Level 3
{} Level 3 was the third attempt at an esolang in the {} family, and the first successful (i.e. nonambiguous) one. It uses an unbounded signed integer accumulator called acc.
Commands
Command  Meaning 

{} 
0 
{{}} 
++acc 
{{x}} 
acc = x 
{xy} 
While acc ≠ x do y (y can be any number of commands > 0) 
Computational class
Level 3 is a pushdown automaton, as its single accumulator can only be incremented.
Level 4
{} Level 4 was the fourth attempt at an esolang in the {} family, and the second successful one. It uses an unbounded signed integer accumulator called acc.
Commands
Command  Meaning 

{} 
1 
{{}} 
acc 
{{x}} 
acc = x 
{{xy}} 
x  y 
{xy} 
While acc ≠ x do y (y can be any number of commands > 0) 
Computational class
{} Level 4 is a pushdown automata, as it has only one accumulator and no instructions to multiply/divide by a constant. (I could be wrong...)
Level 5
{} Level 5 was the fifth attempt at an esolang in the {} family, and the third successful one. It uses an array of unbounded signed integer registers called accs (the array is called accs). The array also has negative indices.
Commands
Command  Meaning 

{} 
1 
{{xy}} 
x  y 
{{{xy}}} 
accs[x] = y 
{{{x}}} 
accs[x] 
{{xyz}} 
While accs[x] != y do z (z can be any number of commands > 0) 
Computational class
{} Level 5's computational class is unknown, and possibly TC.
Level 6
{} Level 6 is the sixth esolang in the {} family, and the fourth successful one. It uses a bit called N and an array of integers called accs.
Commands
Command  Meaning 

{} 
1 
{{}} 
Nop 
{{{x}}} 
accs[N] += x 
{{xy}} 
x  y 
{xy} 
While accs[N] ≠ x do y (y can be any number of commands > 0) 
After each command, N is swapped between 0 and 1.
Computational class
Level 6 has an unknown computational class, although by padding with nops, it could possibly be used to write programs.
Level 7
{} Level 7 is the seventh esolang in the {} family, and the fifth successful one. It uses a bit called N and an array of unbounded signed integers (the array is called accs).
Commands
Command  Meaning 

{} 
1 
{{}} 
accs[N] 
{{x}} 
While accs[N] ≠ 0 do x (x can be any number of commands > 0 and ≠ 2) 
{{xy}} 
x  y 
{xy} 
x + y 
After each command, N is swapped between 0 and 1.
Computational class
Level 7 is Turingcomplete, as it could simulate a tworegister Minsky machine. (You can use {}
on its own as a nop.)
Level 8
{} Level 8 is a brainfuck equivalent, making it the first esolang in the {} family known to be Turingcomplete.
Commands
Level 8  Brainfuck 

{} 
+

{{}} 


{{}{}} 
>

{{}{}{}} 
<

{{}{}{}{}} 
,

{{}{}{}{}{}} 
.

{{p}} 
[p]

Computational class
Since Level 8 is a brainfuck equivalent, it is Turingcomplete.