Compilation error using Forest package

I’ve been looking at this for a while, but can’t figure out what’s wrong with the code. It compiles in Overleaf, but with errors. I’ll show the code first, and then the errors.

documentclass{article}
usepackage[utf8]{inputenc}
usepackage[dvipsnames]{xcolor}
definecolor{mygreen}{rgb}{0,0.4,0}

newcommand{both}{$punderline{q}$}
newcommand{onlyP}{$p underline{neg q}$}
newcommand{onlyQ}{$neg punderline{q}$}
newcommand{neither}{$neg punderline{neg q}$}

usepackage{forest}
forestset{
sn edges/.style={for tree={circle, draw, thick, minimum size=1cm,inner sep=1,edge={->,thick}}}
}

title{forest_test.tex}

begin{document}
begin{forest}
sn edges
[, phantom, s sep = 0.6cm
    [both, mygreen, name=level0
        [both, mygreen, edge=mygreen, name=level10, edge label = {node [midway,left] {$a$} }
            [onlyP, red, edge=red, edge label = {node [midway,left] {$a$} }, name=level20]
            [neither, red, edge=red, edge label = {node [midway, right] {$a$} }, name=level21] 
        ]
        [onlyQ, mygreen, edge=mygreen, edge label = {node [midway,right] {$a$}}, name=level11
            [onlyP, mygreen, edge=mygreen, edge label = {node [midway,left] {$a$}},name=level22  [both, mygreen, edge=mygreen,name=h1, edge label = {node [midway,left] {$a$}} [both, red, edge=red, edge label = {node [midway,left] {$a$}}] [onlyQ, mygreen, edge=mygreen, edge label = {node [midway,right] {$a$}},name=h1new]] [onlyQ, mygreen, edge=mygreen, name=h2, edge label = {node [midway,right] {$a$}} [both, red, edge=red, edge label = {node [midway,left] {$a$}}] [onlyQ, red, edge=red, edge label = {node [midway,right] {$a$}}] ]] 
            [neither, mygreen, edge=mygreen , edge label = {node [midway,right] {$a$}}, name=level23 [both, mygreen, edge=mygreen,name=h3new1, edge label = {node [midway,left] {$a$}} [both, red, edge=red, edge label = {node [midway,left] {$a$}}] [onlyQ, mygreen, edge=mygreen, edge label = {node [midway,right] {$a$}}, name=h2new] ] [onlyQ, mygreen, edge=mygreen,name=h4, edge label = {node [midway,right] {$a$}} [both, red, edge=red, edge label = {node [midway,left] {$a$}}] [onlyQ, red, edge=red, edge label = {node [midway,right] {$a$}}]]] 
        ]   
    ]
    
    [onlyQ, mygreen, name=level00
        [both, mygreen, edge=mygreen,edge label = {node [midway,left] {$a$}}, name=level12
            [onlyP, mygreen, edge=mygreen,edge label = {node [midway,left] {$a$}}, name=level24 [both, mygreen, edge=mygreen,name=h5,edge label = {node [midway,left] {$a$}} [both, red, edge=red, edge label = {node [midway,left] {$a$}}] [onlyQ, red, edge=red, edge label = {node [midway,right] {$a$}}]] [onlyQ, mygreen, edge=mygreen,name=h6,edge label = {node [midway,right] {$a$}} [both, mygreen, edge=mygreen, edge label = {node [midway,left] {$a$}},name=h3new] [onlyQ, red, edge=red, edge label = {node [midway,right] {$a$}}] ]] 
            [neither, name=level25, mygreen, edge=mygreen,edge label = {node [midway,right] {$a$}} [both, mygreen, edge=mygreen,name=h7,edge label = {node [midway,left] {$a$}} [both, red, edge=red, edge label = {node [midway,left] {$a$}}] [onlyQ, red, edge=red, edge label = {node [midway,right] {$a$}}]] [onlyQ, mygreen, edge=mygreen,name=h8,edge label = {node [midway,right] {$a$}} [both, mygreen, edge=mygreen, name=h4new, edge label = {node [midway,left] {$a$}}] [onlyQ, red, edge=red, edge label = {node [midway,right] {$a$}}]]] 
        ]
        [onlyQ, mygreen, edge=mygreen,edge label = {node [midway,right] {$a$}}, name=level13
            [onlyP,name=level27, red, edge=red,edge label = {node [midway,left] {$a$}}] 
            [neither,name=level28, red, edge=red ,edge label = {node [midway,right] {$a$}}] 
        ]
    ]
]
end{forest}

end{document}

The intended output is:

The errors I get are:

     main.tex, line 44
Runaway argument?
{,afterthought={ 
! Paragraph ended before forestOappto was complete.
<to be read again> 
                   par 
l.44 end{forest}
                 
I suspect you've forgotten a `}', causing me to apply this
control sequence to too much text. How can we recover?
My plan is to forget the whole thing and hope for the best.
 main.tex, line 44
Extra }, or forgotten endgroup.
<argument> ...iven options}{,afterthought={ par }
                                                  }
l.44 end{forest}
                 
I've deleted a group-closing symbol because it seems to be
spurious, as in `$x}$'. But perhaps the } is legitimate and
you forgot something else, as in `hbox{$x}'. In such cases
the way to recover is to insert both the forgotten and the
deleted material, e.g., by typing `I$}'.
 main.tex, line 44
Extra }, or forgotten endgroup.
<argument> ...ven options}{,afterthought={ par }}
                                                  
l.44 end{forest}
                 
I've deleted a group-closing symbol because it seems to be
spurious, as in `$x}$'. But perhaps the } is legitimate and
you forgot something else, as in `hbox{$x}'. In such cases
the way to recover is to insert both the forgotten and the
deleted material, e.g., by typing `I$}'.

documentclass[dvipsnames, margin=3mm]{standalone}% that whole image can be seen

newcommand{both}{$punderline{q}$}
newcommand{onlyP}{$p underline{neg q}$}
newcommand{onlyQ}{$neg punderline{q}$}
newcommand{neither}{$neg punderline{neg q}$}

usepackage{forest}
usetikzlibrary{arrows.meta}
definecolor{mygreen}{rgb}{0,0.4,0}
tikzset{
ELS/.style = {% Edge Label Style
              pos=0.4, node font=footnotesize, 
              inner sep=2pt, anchor=#1},
        }
newcommandEC[1]{#1, edge=#1}


begin{document}
    begin{forest}
for tree = {% nodes
            circle, draw, semithick,
            minimum size=10mm, inner sep=0pt,
            % tree
            edge={-Straight Barb, semithick},
            s sep = 2mm,
            },% end for tree
EL/.style={% Edge Label, automatic positioning
           if n=1{edge label={node[ELS=east]{$#1$}}}
                 {edge label={node[ELS=west]{$#1$}}}
          },
EC/.style={color=#1, edge=#1}% coloring nodes and edges
[, phantom, 
% left tree
    [both, EC=mygreen
        [both, EC=mygreen, EL=a
            [onlyP, EC=mygreen,  EL=a
                [neither, EC=red, EL=a]
            ]
        ]
        [onlyQ, EC=mygreen, EL=a
            [onlyP, EC=mygreen, EL=a
                [both,  EC=mygreen, EL=a
                    [both,  EC=red,     EL=a]
                    [onlyQ, EC=mygreen, EL=a]
                ] 
                [onlyQ, EC=mygreen, EL=a
                    [both, EC=red,  EL=a] 
                    [onlyQ, EC=red, EL=a] 
                ]
            ]
            [neither, EC=mygreen, EL=a
                [both, EC=mygreen,EL=a
                    [both, EC=red, EL=a] 
                    [onlyQ, EC=mygreen, EL=a] 
                ]
                [onlyQ, EC=mygreen, EL=a
                    [both, EC=red,  EL=a]
                    [onlyQ, EC=red, EL=a]
                ]
            ]
        ]
    ]
% right tree
    [onlyQ, EC=mygreen, 
        [both, EC=mygreen, EL=a
            [onlyP, EC=mygreen, EL=a
                [both, EC=mygreen,  EL=a
                    [both, EC=red,  EL=a] 
                    [onlyQ, EC=red, EL=a]
                ] 
                [onlyQ, EC=mygreen, EL=a
                    [both, EC=mygreen, EL=a] 
                    [onlyQ, EC=red,    EL=a] 
                ]
            ]
            [neither, EC=mygreen,EL=a
                [both, EC=mygreen, EL=a
                    [both, EC=red, EL=a] 
                    [onlyQ, EC=red, EL=a]
                ] 
                [onlyQ, EC=mygreen,EL=a
                    [both, EC=mygreen, EL=a] 
                    [onlyQ, EC=red,    EL=a]
                ]
            ]
        ]
        [onlyQ, EC=mygreen,  EL=a
            [onlyP,EC=red,   EL=a]
            [neither,EC=red, EL=a]
        ]
    ]
]
    end{forest}
end{document}