diff --git a/2021/10/data b/2021/10/data
new file mode 100644
index 0000000..e7b770e
--- /dev/null
+++ b/2021/10/data
@@ -0,0 +1,98 @@
+{<[[<<<[[{[[<<()()>>[([]<>){{}{}}]]]<(<{{}<>}{{}{}}><{<>[]}[{}{}]>)({(())}<[(){}][(){}]>)>}]<<<(<<{}
+{[({({([({(((<[]()>[()<>]){[<>[]](<>[])})<<<[]()}>(<()()>)>)}[{((<{}[]>{<>()}){[<>{}]<<><>>})(({[]()}<<>()>)<
+(((([{{{<{<[[<()<>><<>{}>]]{<(<>())>}>{<[([]<>)<{}{}>][[<><>][<>[]]]>[{(<>{})[<>()]}<<()[]>[[]<
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+<[(({[({<<[[[{<>{}}(<><>))<(<>[])[{}[]]>]<[([][])[(){}]]>]([<[()()](<>[])>]<(<{}()>[{}<>])({<>[
+(<[[{[[[(<((<<{}{}><[]<>>><[{}<>][<>[]]>)<(<{}<>><{}{}>)[{()[]}<<>()>]>)>[(<{({}{})}[{()[]}{[]<>}]>){<(([]
+(([[({{{(<([({[]{}}){{[][]]}])>)[<([[[{}]{(){}}][([]())]]([{[][]}{<>()}](({}()){<>{}})))[{({
+{(<<([([(<<[{((){})([]<>)}]<{{{}{}}{{}[]}}<{(){}}{()[]})>><([<[]{}>([]<>)](<()<>>)){<([]<>
+{[<<[<{{((({<[[]{}]{{}}>{<{}<>>[<>[]]}})<{[(<><>><{}<>>][{[]{}}]}[[[[][]]<<>{}>]{[[]()][[]<>]}]>)[(
+({<(<([{<{<[(((){}){(){}})]>}[{{{{()()}<[]()>}{{<>()}<{}{}>}}[[{{}{}}[<><>]]{({}[]>[[]{}]}]}({{{()()
+{[[{([{<<{<(<<{}()>[()]>)<{{()()}}[<[][]>(<>{})]>>{[<{<>()){()<>}>{{()()}[<>()]}][[[{}[]]]<{{}[]}<()(
+{{<<<<<[[([{<[{}[]]{()<>}>{<<>()>{{}<>}}}<<{{}()}{()()}>{[()<>]({}[])]>]{[(<{}{}>)<({}[])>]<{({}<>)}{({}())
+({(<<{[<<{<(<[<>()][[][]]><[{}<>]({}[])>)[[[<>[]][[]()]]<{[]{}}[{}{}]>]>{[(<[]()>{<>{}})][<{{}}<{
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+{{{[<[([<(<{[([][])[{}[]]]{[()()]{{}()}}}><[<([][])(<>())><{()[]}({}<>)>]<<<(){}><<><>>>((()()){
+[(((([{({<(<(<[]<>>{()[]})><{(<><>){{}[]}}{(()<>)([][])}>)>})}][({{[[{<(<><>){{}()}>((<>()){<>[]
+([{<{<({(<[(<({}<>)><{[]}[{}[]]>)(<[[][]]{[]{}}>{{[]}((){})})]{(((()){{}()})(([][])({}{})))[(<()[]><(
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+{(({({[{{((<[([]())((){})]>){[{(<>[])}<([]{})[[]<>]>]({<()<>>[[]<>]}[<()>{<>[]}])})({<([[][]]((){}))([<>{}])
+<(<(<<{[<<{<<[()[]][[]()]><([][])<{}()>>}}>[<<<<{}<>>>{[{}][{}{}]}>[<[()()]{{}[]}>[{[][]}([])]]>[[<<[][]>(
+<<{{({<<(([{{([][])(()<>)}}(<<[]{}>>)])([{[(()[])]}<{{<><>}<[]<>>}[<{}<>><[]<>)]>]{{<[{}[]]
+({[[[[(([[[{<({})([]())>{{<>{}}}}][[<<[]>[<>()]>]{[[[]<>][<>{}]]{[<>[]]}})][[<(<(){}>{()[]})><[[()[
+(((((([{{{(<<(<>{}){<>}><(()[])<()[]>>>{[<{}<>>(<>())}<{{}()}>})((([(){}]{<>})[{[]{}}{{}[]
+(([([(((<[(({[<>()]{[][]}})[{{[]()>[[]{}]}(<<>{}><{}<>>)]){[({[]}(<>[]))([()()][<>{}])]({({}
+[(<({{([[<(((<<>()>[[]<>])({{}()}<()<>>))[[{[]()}<()<>>][{()()}<{}[]>]])>({(<({}{})<()[]}>[{()
+{{{[([<{{{([<<<>{}>{()<>}>{<{}()><<><>>}]([{()}]))<{[<()()>{()[]}]{({}[])[<>()]}}>}}}({<(({({
+[([([<[<(<[{{{<>()}{()[]}}({()[]}[{}<>])}{[{<>}]([[][]]<(){}>)}]>[[{<[<>()][{}()]>(((){}>[<>[]])}{{{<>(
+{{[{{[[<{(<([[[][]]([]<>)])>)<{<<{<>()}[<>()]><((){})<<><>>>>([<<><>>(()<>)]([(){}}{[]<>}))}>}(({{{{[]}{
+[[[[({[<({{[[(<><>)]{<<>[]>([]{})}]<[{[]}{()()}]([<>()]([]<>>)>}})>{{<([{<{}{}>{()}}])({<[<>()](<><>)>
+{[({<[({[{[({[{}()][[]<>]}((()<>)<{}<>>))<[{{}}({}{})]>]{[<<<>[]>[[][]]>(({}[])(()[]))>{(([]{})({}[]))([
+[<<([{{(<<[<[[{}[]]](<[]{}>[<>{}])>[[<{}[]>(<>[])]{([][])[()[]]}]][[{{()[]}[<>{}]}(<<>{}>[[]
+<[(([{([([<{[[(){}]<<>{}>]}[[[()()]{{}<>}]]>[[{({}{})[()()]}([()()][<>[]])]{<[[]<>][[][]]>}]]{{<{[<>
+[<[[[[([[{[[<[{}{}]([]<>)>[({}[])<[]<>>]][<{()()}[<>[]]>([[]]<<><>>)]]}([<{{{}[]}}{(()<>>({}[
+<[<{[(<{({[<[[[][]]([][])]<([]){{}<>}>>[({<>{}}<[]>)]]([[([]{})[[]()]][[[]{}]({}{})]](<[{}<>
+({[<([(<[[<([[(){}]<<>{}>])({[[]{}]<()[]>}<<[]<>>{[][]}>)>{<[<[]()><{}[]>]([<>()]({}[]))><(
+({<<<{<({[[{[{<>{}}[<><>]]}{(({})[()()])<<()<>>([]{})>}]]]{<{{([[]<>](<>[]))[[{}()]({}())]}}>((<([{}<>])>{{<[
+[{([{[[{{<{<[{[]()}<[]{}>]>({<{}[]>{<>[]}})}[(({{}<>}<{}<>]){[[]{}]({}[])})]>}}]({([[([<()()>{[]
+<[{([([{[{<(([<>[]]{<>()})<{{}<>}>){([<><>])<(()[])<<>{}>>}><{{[{}<>]{<>}}[(())[()<>]]}<{[{}{}]{{}{}}}<{{}<>
+[{<<([{{(((<{<<>()>[{}()]}>{<<<>[]><[]()>>}){[(([][])([]()))<{{}[]}[[]()]>][[{{}<>}({}{})]{({}{})(<
+{({[((<([[[{{([])[()()]}({{}{}}))<(<[]<>>[()[]])>]<<([[]<>])<[<>()][[]<>]>>({[<><>]{{}[]}}({()[]
+{[(<(<{[({[(<<[]>{<>{}}>[{<><>}([]())])(<[[][]]<()<>>>[(()[])])]<{[{()[]}[<>{}]]}[{<(){}>(<>{})}<<<>()>>]
+(<{<[<({{{{([({}{})[[]{}]]({{}<>}<()[]}))}(<<{<>()}{()<>}>{[<>{}][()[]]}>{<<[][]>{<>()}><(<>{})<{}[]>>})}
+{(<<{[({<<[(<{{}{}}<[]<>>>((<>())([]<>)))]>><<({<{[]<>}([]<>)>{[()()]}}<<{{}<>}<()()>>(<()()
+<([([<(<[({[[({}()){()<>}](({}{})(<><>))][{({}<>)<{}{}>}{([]){(){}}}]})]>)<[[{<{{(()){<>[]}}({{}()}
+<<<([{[({{{((<{}()>{()()})[[<>()]])[[[{}()]<{}()>]{{[]<>}{{}())}]}<<{<<>><<><>>}[{{}[]}(<><>)
+<([<[<{[[[{[{[<><>][{}<>]}(<[]{}>)]}([{{<>()}<{}[]>}{([]<>)[(){}]}]<{((){})<[]()>}[<[]()><()[]>]>
+[([[[[[({{[(<[{}<>]<{}()>><[<><>]{<>()}>)]}<{(<(()<>)<{}{}>>{{()<>}(()()}})}>})(<[<([<<>[]>((){})]([[]<>]<()
+{(<[[{(((([[([{}()]<{}()))[({}{}){[]}]](<<<>[]>>([<>{}]))][(<({}{})<()[]>><<[]{}><{}[]>>)])(<([([][])[
+({(([{{<{{{<[<<>[]>{()<>}][([][]){()<>}]>([<()>(<><>)]<{<><>}<[]>>)}<{[[<>[]][<>{}]]<{<>()}{[][]
+{[([[[(([<{<{[[]<>]<<>()>}<<()()>([]{})>>[<<()[]>(<>())>[(()<>)]]}>]{{({{{{}[]}({})}<{{}<>}[[]()]>}((
+[<([[<[{{{[[[<<>{}>]{<()[]>{[]<>}}]{([[]{}]({}()))}]}}}(<{<[[({}{})<()()>]]({({}<>)[[]]}{[<><>]{<>{}}})>(<[
+<<(<<{{(({<[<<[]{}>{()()}}[[()[]]]]{[(<>{}){<>}]{[{}](<>)}}><{<(()())<[]<>>>[<(){}>(<>[])]
+{<(<[<[(((<{((()[])([]<>))([[]<>]({}[]))}><<([<>())<[]<>>)(<{}[]>({}<>))>[[([]())]({()()}{{}<>})
+[[((<[[[{{<{<{{}()}[{}()]>{{[]{}}[<><>]}}>}<{[<[(){}]<<><>>]([{}<>]<<><>>)]}(<<[{}<>]<<>{}>
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+{<[({(<{{[([{{[]{}}((){})}[[{}[]]<{}()>]]((<[]<>>)<([]()){{}[]}>))(<<{()[]}{[]})>[[(()())]{[()<>][<>(
+<<{[[[[{<({<[[{}()]]{{[]<>}{[]}}><{{{}()}({}{})}>}{([({}[])({}())](({}[])))[<{[]<>}[<>()]><<[]<>>(<>[])>]}
+[(([<<[{[{<({{()[]}<<><>>})[[([]())[[]{}])(<<>{}>)]>(<{{[][]}[{}()]}([{}{}][(){}])>((<<>[]>(()
+[({<<[[<{[<<({[]()}<()<>>)>]]{{<[[[]][{}<>]]>}{([[<>{}][{}{}]]<((){})(()[])>)}}}([{((<{}[]>)[<{}[]><{}()>])}
+{[[((<[{<<([{<<><>>([]{})}<(<><>)<<>()>>][{[[]{}]{()()}}<({}{})([][])>])><<{({<>{}}[<>()])((
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+{([<{[<({{{({[[][]][()()])[<<>()><[][]>])}<{{{[]()}[{}()]}{{<>()}{<>}}}((({}())<{}{}>){(<>{})[<>{}]})>}})(((
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+<(<[[[<<{([<<[[]<>]{<>[]}><{()()}([]<>)>>]{<{(<>())((){})}{[{}{}]<<>{}>}>})({([[{}{}]])[(<<>()>[
+{[(<{<[[{<{{(<()[]><<>{}>){[()<>]<{}<>>}}[[[<>{}][[]<>]]]}<[[({})<<>[]>]]{{<()<>><<>[]>}<{()[]}((){}
+({[{(<<{[<{({[()()]{{}}}<({}{}){()()}>)}<{(({}{})[<>[]]){([]())[[][]]}}{(<[]<>)[()])[[<>()]]}>>
+(({<<[<[<<<({<{}[]>({}{})}{<{}[]><{}[]>})>>(<<(<()()>{[]{}})({()<>}[()()])>[{[{}()][[]]}({<>()}}]>(
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+([[[<(<{[({<({()()}{<>()})((<>[])<[]<>>)>}<{<<{}()><<>>>}({{{}[]}}[(()[])[()<>]])>)<[<((()())[<>{}])(
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+<[{[<[{[({{<(({}<>}[[]()])>({{[][]}}<[(){}](()[])>)}})([[{{<<>()>([]{})}[<<>{}>[<><>]]}]])]
+{(<{([{[[({[(<[]{}>)({{}[]}{()()}))<{(()[])}[[()()]{{}[]}]>}<{<(()<>)>{{[]{}}({}())}}({{{}[]}{<
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+<(<(<[([<[{[<(()<>)<()[]>><(<>())([][])>]{<[{}<>]{{}()}>{[[]{}](<>{})}}}<[<([]{})><{{}<>}([]())>]>]>
+<<<(<<[({{{<{({}<>)<()[]>}<[()<>]{(){}}>><{[[]()]<[]{}>}[({}{})<(){}>]>}(<[<<>[]>{()[]}]>)}[<{[<{}>[{}{
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+[<<[{{(({({<{{{}{}}{<>[]}}({[][]}{<>[]})>[{[{}<>][<>[]]}[({}[])[[]<>]]]})}))<(<[[<(({}()))[<<>()>{(
+{<<([<{({[{{[({}[])<<>{}>]([()<>]<(){}>)}<([{}[]]({}{}))>}[<<<<>{}>[[][]]>{<<>[]><()>}>[<<<>><[][]>
+[({(<({[<[{{[<<>[]>[()[]]]<<<>[]>>}}<{([{}[]](<>{}))[{<>}{{}<>}]}(<<[][]>>[{[]<>}])>]>[(<(({<>[]}{<><>}))(<
+{<[[{{<<{(<(<([]<>)[[][]]>[([]{})[<>{}]])<[{<>()}{[]<>}]>>>[{(({()()}[<>[]]){({}())<[]<>>})}[(<{<>
+{[[{{{<[<[{<(({}{})[{}()])[(<><>)({}())]>}{[<{[]{}}[()[]]>]<{[()()]<[]()>}<[[][]]>>}]>{{({{{()[]}{{}(
+<{[<([{{[[<(<{<><>}[{}{}]><((){})>){[[()()][()[]]]{[[]<>]}}>]<<(<({}[])<{}[]>>{(<><>)<[]()>}){(<
\ No newline at end of file
diff --git a/2021/10/example_data b/2021/10/example_data
new file mode 100644
index 0000000..2f182d8
--- /dev/null
+++ b/2021/10/example_data
@@ -0,0 +1,10 @@
+[({(<(())[]>[[{[]{<()<>>
+[(()[<>])]({[<{<<[]>>(
+{([(<{}[<>[]}>{[]{[(<()>
+(((({<>}<{<{<>}{[]{[]{}
+[[<[([]))<([[{}[[()]]]
+[{[{({}]{}}([{[{{{}}([]
+{<[[]]>}<{[{[{[]{()[[[]
+[<(<(<(<{}))><([]([]()
+<{([([[(<>()){}]>(<<{{
+<{([{{}}[<[[[<>{}]]]>[]]
\ No newline at end of file
diff --git a/2021/10/main.py b/2021/10/main.py
new file mode 100644
index 0000000..1ac25ac
--- /dev/null
+++ b/2021/10/main.py
@@ -0,0 +1,34 @@
+openers = ['(', '[', '{', '<']
+closers = [')', ']', '}', '>']
+points = [3, 57, 1197, 25137]
+
+score = 0
+with open('data', 'r') as fp:
+    # NOTE(dev): We assume all lines are the same length
+    for line in fp:
+        stack = []
+        for ch in line.strip():
+            line_score = 0
+            if(ch in openers):
+                stack.append(ch)
+            elif(len(stack) == 0):
+                try:
+                    i = closers.index(ch)
+                    line_score += points[closers.index(ch)]
+                except ValueError: # not a closer
+                    pass
+            else:
+                try:
+                    i = closers.index(ch)
+                    last = stack[-1]
+                    stack.pop()
+                    if(last != openers[i]):
+                        line_score += points[i]
+                        score += line_score
+                        print(last, '!=', openers[i])
+                        break
+                except ValueError: # not an opener or closer!
+                    pass
+            score += line_score
+
+print(score)
diff --git a/2021/10/main2.py b/2021/10/main2.py
new file mode 100644
index 0000000..c31ec54
--- /dev/null
+++ b/2021/10/main2.py
@@ -0,0 +1,33 @@
+openers = ['(', '[', '{', '<']
+closers = [')', ']', '}', '>']
+points = [3, 57, 1197, 25137]
+
+scores = []
+with open('data', 'r') as fp:
+    # NOTE(dev): We assume all lines are the same length
+    for line in fp:
+        stack = []
+        corrupt = False
+        for ch in line.strip():
+            if(ch in openers):
+                stack.append(ch)
+            else:
+                try:
+                    i = closers.index(ch)
+                    last = stack[-1]
+                    stack.pop()
+                    if(last != openers[i]):
+                        corrupt = True
+                        break
+                except ValueError: # not an opener or closer!
+                    pass
+        if(not corrupt and len(stack)):
+            line_score = 0
+            for ch in reversed(stack):
+                line_score *= 5
+                line_score += openers.index(ch) + 1
+            scores.append(line_score)
+
+scores.sort()
+print('scores[int(', len(scores), '/ 2 )]')
+print(scores[int(len(scores) / 2)])