diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..ebeda5b
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,25 @@
+name: CI
+on:
+  pull_request:
+    branches: [ main ]
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  compat:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        zig: [ 0.6.0, 0.7.0, 0.8.0, 0.9.0, 0.10.0 ]
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Setup Zig
+      uses: goto-bus-stop/setup-zig@v2
+      with:
+        version: ${{ matrix.zig }}
+
+    - name: Check compatibility with old Zig compilers
+      run: ci/compat.sh
diff --git a/ci/compat.sh b/ci/compat.sh
new file mode 100755
index 0000000..f5895fd
--- /dev/null
+++ b/ci/compat.sh
@@ -0,0 +1,25 @@
+#!/bin/bash
+# This script checks that `zig build` will return an useful error message when
+# the Zig compiler is not compatible, instead of failing due to a syntax error.
+#
+# This script should be run on an UNIX system.
+
+zig_version=$(zig version)
+
+zig build -Dn=1 -Dhealed &> /dev/null 2>&1
+zig_ret=$?
+
+if [ "$zig_ret" -eq 0 ]; then
+    printf "zig %s unexpectedly succeeded\n" "$zig_version"
+    exit 1
+fi
+
+zig_error=$(zig build -Dn=1 -Dhealed 2>&1)
+
+echo "$zig_error" | grep -q "it looks like your version of zig is too old"
+zig_ret=$?
+
+if [ "$zig_ret" -ne 0 ]; then
+    printf "zig %s is not compatible\n" "$zig_version"
+    exit 1
+fi
diff --git a/exercises/058_quiz7.zig b/exercises/058_quiz7.zig
index 3069710..1ceac5a 100644
--- a/exercises/058_quiz7.zig
+++ b/exercises/058_quiz7.zig
@@ -107,7 +107,7 @@ const Path = struct {
 const a_paths = [_]Path{
     Path{
         .from = &a, // from: Archer's Point
-        .to = &b,   //   to: Bridge
+        .to = &b, //   to: Bridge
         .dist = 2,
     },
 };
@@ -115,12 +115,12 @@ const a_paths = [_]Path{
 const b_paths = [_]Path{
     Path{
         .from = &b, // from: Bridge
-        .to = &a,   //   to: Archer's Point
+        .to = &a, //   to: Archer's Point
         .dist = 2,
     },
     Path{
         .from = &b, // from: Bridge
-        .to = &d,   //   to: Dogwood Grove
+        .to = &d, //   to: Dogwood Grove
         .dist = 1,
     },
 };
@@ -128,12 +128,12 @@ const b_paths = [_]Path{
 const c_paths = [_]Path{
     Path{
         .from = &c, // from: Cottage
-        .to = &d,   //   to: Dogwood Grove
+        .to = &d, //   to: Dogwood Grove
         .dist = 3,
     },
     Path{
         .from = &c, // from: Cottage
-        .to = &e,   //   to: East Pond
+        .to = &e, //   to: East Pond
         .dist = 2,
     },
 };
@@ -141,17 +141,17 @@ const c_paths = [_]Path{
 const d_paths = [_]Path{
     Path{
         .from = &d, // from: Dogwood Grove
-        .to = &b,   //   to: Bridge
+        .to = &b, //   to: Bridge
         .dist = 1,
     },
     Path{
         .from = &d, // from: Dogwood Grove
-        .to = &c,   //   to: Cottage
+        .to = &c, //   to: Cottage
         .dist = 3,
     },
     Path{
         .from = &d, // from: Dogwood Grove
-        .to = &f,   //   to: Fox Pond
+        .to = &f, //   to: Fox Pond
         .dist = 7,
     },
 };
@@ -159,20 +159,20 @@ const d_paths = [_]Path{
 const e_paths = [_]Path{
     Path{
         .from = &e, // from: East Pond
-        .to = &c,   //   to: Cottage
+        .to = &c, //   to: Cottage
         .dist = 2,
     },
     Path{
         .from = &e, // from: East Pond
-        .to = &f,   //   to: Fox Pond
-        .dist = 1,  // (one-way down a short waterfall!)
+        .to = &f, //   to: Fox Pond
+        .dist = 1, // (one-way down a short waterfall!)
     },
 };
 
 const f_paths = [_]Path{
     Path{
         .from = &f, // from: Fox Pond
-        .to = &d,   //   to: Dogwood Grove
+        .to = &d, //   to: Dogwood Grove
         .dist = 7,
     },
 };
@@ -355,8 +355,8 @@ pub fn main() void {
     // Here's where the hermit decides where he would like to go. Once
     // you get the program working, try some different Places on the
     // map!
-    const start = &a;        // Archer's Point
-    const destination = &f;  // Fox Pond
+    const start = &a; // Archer's Point
+    const destination = &f; // Fox Pond
 
     // Store each Path array as a slice in each Place. As mentioned
     // above, we needed to delay making these references to avoid
diff --git a/exercises/059_integers.zig b/exercises/059_integers.zig
index 5a6295d..a497efa 100644
--- a/exercises/059_integers.zig
+++ b/exercises/059_integers.zig
@@ -18,10 +18,10 @@
 const print = @import("std").debug.print;
 
 pub fn main() void {
-    var zig = [_]u8 {
-        0o131,     // octal
+    var zig = [_]u8{
+        0o131, // octal
         0b1101000, // binary
-        0x66,      // hex
+        0x66, // hex
     };
 
     print("{s} is cool.\n", .{zig});
diff --git a/exercises/069_comptime4.zig b/exercises/069_comptime4.zig
index 004a42c..f4c8bbb 100644
--- a/exercises/069_comptime4.zig
+++ b/exercises/069_comptime4.zig
@@ -16,7 +16,7 @@ const print = @import("std").debug.print;
 pub fn main() void {
     // Here we declare arrays of three different types and sizes
     // at compile time from a function call. Neat!
-    const s1 = makeSequence(u8, 3);  // creates a [3]u8
+    const s1 = makeSequence(u8, 3); // creates a [3]u8
     const s2 = makeSequence(u32, 5); // creates a [5]u32
     const s3 = makeSequence(i64, 7); // creates a [7]i64
 
diff --git a/exercises/075_quiz8.zig b/exercises/075_quiz8.zig
index c2dbc1a..d54864c 100644
--- a/exercises/075_quiz8.zig
+++ b/exercises/075_quiz8.zig
@@ -151,8 +151,8 @@ const HermitsNotebook = struct {
 };
 
 pub fn main() void {
-    const start = &a;        // Archer's Point
-    const destination = &f;  // Fox Pond
+    const start = &a; // Archer's Point
+    const destination = &f; // Fox Pond
 
     // We could either have this:
     //
diff --git a/exercises/083_anonymous_lists.zig b/exercises/083_anonymous_lists.zig
index 838d40e..daaeaff 100644
--- a/exercises/083_anonymous_lists.zig
+++ b/exercises/083_anonymous_lists.zig
@@ -18,8 +18,8 @@ pub fn main() void {
     //
     // Don't change this part:
     //
-    //     = .{'h', 'e', 'l', 'l', 'o'};
+    //     = .{ 'h', 'e', 'l', 'l', 'o' };
     //
-    const hello = .{'h', 'e', 'l', 'l', 'o'};
+    const hello = .{ 'h', 'e', 'l', 'l', 'o' };
     print("I say {s}!\n", .{hello});
 }
diff --git a/exercises/092_interfaces.zig b/exercises/092_interfaces.zig
index 43f1119..5ac5768 100644
--- a/exercises/092_interfaces.zig
+++ b/exercises/092_interfaces.zig
@@ -99,7 +99,7 @@ pub fn main() !void {
     var my_insects = [_]Insect{
         Insect{ .ant = Ant{ .still_alive = true } },
         Insect{ .bee = Bee{ .flowers_visited = 17 } },
-        Insect{ .grasshopper = Grasshopper{ .distance_hopped = 32 }, },
+        Insect{ .grasshopper = Grasshopper{ .distance_hopped = 32 } },
     };
 
     std.debug.print("Daily Insect Report:\n", .{});
diff --git a/patches/eowyn.sh b/patches/eowyn.sh
index a30a67a..a036acf 100755
--- a/patches/eowyn.sh
+++ b/patches/eowyn.sh
@@ -42,5 +42,8 @@ do
     fi
 done
 
+# Check the healed exercises formatting.
+zig fmt --check patches/healed
+
 # Test the healed exercises. May the compiler have mercy upon us.
 zig build -Dhealed
diff --git a/patches/patches/024_errors4.patch b/patches/patches/024_errors4.patch
index 5996a99..48e0821 100644
--- a/patches/patches/024_errors4.patch
+++ b/patches/patches/024_errors4.patch
@@ -5,6 +5,6 @@
 >         if (err == MyNumberError.TooSmall) {
 >             return 10;
 >         }
->  
+> 
 >         return err;
 >     };
diff --git a/patches/patches/026_hello2.patch b/patches/patches/026_hello2.patch
index 0065da5..e97a7b5 100644
--- a/patches/patches/026_hello2.patch
+++ b/patches/patches/026_hello2.patch
@@ -1,4 +1,4 @@
-22c22
+26c26
 <     stdout.print("Hello world!\n", .{});
 ---
 >     try stdout.print("Hello world!\n", .{});
diff --git a/patches/patches/029_errdefer.patch b/patches/patches/029_errdefer.patch
index f93c56f..aa42279 100644
--- a/patches/patches/029_errdefer.patch
+++ b/patches/patches/029_errdefer.patch
@@ -1,4 +1,4 @@
-35c34
+35c35
 <     std.debug.print("failed!\n", .{});
 ---
 >     errdefer std.debug.print("failed!\n", .{});
diff --git a/patches/patches/040_pointers2.patch b/patches/patches/040_pointers2.patch
index a69cb20..87291c3 100644
--- a/patches/patches/040_pointers2.patch
+++ b/patches/patches/040_pointers2.patch
@@ -1,4 +1,4 @@
-24c24
+26c26
 <     const b: *u8 = &a; // fix this!
 ---
 >     const b: *const u8 = &a; // fix this!
diff --git a/patches/patches/046_optionals2.patch b/patches/patches/046_optionals2.patch
index 8437cdc..89fa604 100644
--- a/patches/patches/046_optionals2.patch
+++ b/patches/patches/046_optionals2.patch
@@ -1,8 +1,8 @@
-24c12
+24c24
 <     tail: *Elephant = null, // Hmm... tail needs something...
 ---
 >     tail: ?*Elephant = null, // <---- make this optional!
-54c42
+54c54
 <         if (e.tail == null) ???;
 ---
 >         if (e.tail == null) break;
diff --git a/patches/patches/050_no_value.patch b/patches/patches/050_no_value.patch
index 79db0a3..7ea4e9e 100644
--- a/patches/patches/050_no_value.patch
+++ b/patches/patches/050_no_value.patch
@@ -6,7 +6,7 @@
 <     var first_line2: Err!*const [21]u8 = ???;
 ---
 >     var first_line2: Err!*const [21]u8 = Err.Cthulhu;
-79,80c79,80
+80,81c80,81
 < fn printSecondLine() ??? {
 <     var second_line2: ?*const [18]u8 = ???;
 ---
diff --git a/patches/patches/059_integers.patch b/patches/patches/059_integers.patch
index 50a89a0..7075ebe 100644
--- a/patches/patches/059_integers.patch
+++ b/patches/patches/059_integers.patch
@@ -1,8 +1,8 @@
 22,24c22,24
-<         0o131,     // octal
+<         0o131, // octal
 <         0b1101000, // binary
-<         0x66,      // hex
+<         0x66, // hex
 ---
->         0o132,     // octal
+>         0o132, // octal
 >         0b1101001, // binary
->         0x67,      // hex
+>         0x67, // hex
diff --git a/patches/patches/064_builtins.patch b/patches/patches/064_builtins.patch
index ebe313d..8a154a4 100644
--- a/patches/patches/064_builtins.patch
+++ b/patches/patches/064_builtins.patch
@@ -1,8 +1,8 @@
-72c72
+67c67
 <     const expected_result: u8 = ???;
 ---
 >     const expected_result: u8 = 0b00010010;
-88c88
+82c82
 <     const tupni: u8 = @bitReverse(input, tupni);
 ---
 >     const tupni: u8 = @bitReverse(input);
diff --git a/patches/patches/065_builtins2.patch b/patches/patches/065_builtins2.patch
index 89fb55f..1b085ef 100644
--- a/patches/patches/065_builtins2.patch
+++ b/patches/patches/065_builtins2.patch
@@ -1,39 +1,20 @@
---- exercises/065_builtins2.zig
-+++ answers/065_builtins2.zig
-@@ -58,7 +58,7 @@
-     // Oops! We cannot leave the 'me' and 'myself' fields
-     // undefined. Please set them here:
-     narcissus.me = &narcissus;
--    narcissus.??? = ???;
-+    narcissus.myself = &narcissus;
- 
-     // This determines a "peer type" from three separate
-     // references (they just happen to all be the same object).
-@@ -70,7 +70,7 @@
-     //
-     // The fix for this is very subtle, but it makes a big
-     // difference!
--    const Type2 = narcissus.fetchTheMostBeautifulType();
-+    const Type2 = Narcissus.fetchTheMostBeautifulType();
- 
-     // Now we print a pithy statement about Narcissus.
-     print("A {s} loves all {s}es. ", .{
-@@ -109,15 +109,15 @@
-     // Please complete these 'if' statements so that the field
-     // name will not be printed if the field is of type 'void'
-     // (which is a zero-bit type that takes up no space at all!):
--    if (fields[0].??? != void) {
-+    if (fields[0].type != void) {
-         print(" {s}", .{@typeInfo(Narcissus).Struct.fields[0].name});
-     }
- 
--    if (fields[1].??? != void) {
-+    if (fields[1].type != void) {
-         print(" {s}", .{@typeInfo(Narcissus).Struct.fields[1].name});
-     }
- 
--    if (fields[2].??? != void) {
-+    if (fields[2].type != void) {
-         print(" {s}", .{@typeInfo(Narcissus).Struct.fields[2].name});
-     }
- 
+61c61
+<     narcissus.??? = ???;
+---
+>     narcissus.myself = &narcissus;
+73c73
+<     const Type2 = narcissus.fetchTheMostBeautifulType();
+---
+>     const Type2 = Narcissus.fetchTheMostBeautifulType();
+112c112
+<     if (fields[0].??? != void) {
+---
+>     if (fields[0].type != void) {
+116c116
+<     if (fields[1].??? != void) {
+---
+>     if (fields[1].type != void) {
+120c120
+<     if (fields[2].??? != void) {
+---
+>     if (fields[2].type != void) {
diff --git a/patches/patches/066_comptime.patch b/patches/patches/066_comptime.patch
index 4828ad6..e7130c2 100644
--- a/patches/patches/066_comptime.patch
+++ b/patches/patches/066_comptime.patch
@@ -1,4 +1,4 @@
-64,65c64,65
+65,66c65,66
 <     var var_int = 12345;
 <     var var_float = 987.654;
 ---
diff --git a/patches/patches/076_sentinels.patch b/patches/patches/076_sentinels.patch
index 3cf4877..55c4c96 100644
--- a/patches/patches/076_sentinels.patch
+++ b/patches/patches/076_sentinels.patch
@@ -1,8 +1,8 @@
-85c84
+85c85
 <             for (???) |s| {
 ---
 >             for (my_seq) |s| {
-97c96
+97c97
 <             while (??? != my_sentinel) {
 ---
 >             while (my_seq[i] != my_sentinel) {
diff --git a/patches/patches/080_anonymous_structs.patch b/patches/patches/080_anonymous_structs.patch
index 6df1890..a94e7b8 100644
--- a/patches/patches/080_anonymous_structs.patch
+++ b/patches/patches/080_anonymous_structs.patch
@@ -1,18 +1,8 @@
---- exercises/080_anonymous_structs.zig
-+++ answers/080_anonymous_structs.zig
-@@ -48,13 +48,13 @@
-     // * circle1 should hold i32 integers
-     // * circle2 should hold f32 floats
-     //
--    var circle1 = ??? {
-+    var circle1 = Circle(i32){
-         .center_x = 25,
-         .center_y = 70,
-         .radius = 15,
-     };
- 
--    var circle2 = ??? {
-+    var circle2 = Circle(f32){
-         .center_x = 25.234,
-         .center_y = 70.999,
-         .radius = 15.714,
+51c51
+<     var circle1 = ??? {
+---
+>     var circle1 = Circle(i32){
+57c57
+<     var circle2 = ??? {
+---
+>     var circle2 = Circle(f32){
diff --git a/patches/patches/083_anonymous_lists.patch b/patches/patches/083_anonymous_lists.patch
index b981909..94b594b 100644
--- a/patches/patches/083_anonymous_lists.patch
+++ b/patches/patches/083_anonymous_lists.patch
@@ -1,4 +1,4 @@
 23c23
-<     const hello = .{'h', 'e', 'l', 'l', 'o'};
+<     const hello = .{ 'h', 'e', 'l', 'l', 'o' };
 ---
->     const hello: [5]u8 = .{'h', 'e', 'l', 'l', 'o'};
+>     const hello: [5]u8 = .{ 'h', 'e', 'l', 'l', 'o' };
diff --git a/patches/patches/096_memory_allocation.patch b/patches/patches/096_memory_allocation.patch
index 5398ce5..fd990b0 100644
--- a/patches/patches/096_memory_allocation.patch
+++ b/patches/patches/096_memory_allocation.patch
@@ -1,4 +1,4 @@
-65c65
+66c66
 <     var avg: []f64 = ???;
 ---
 >     var avg: []f64 = try allocator.alloc(f64, arr.len);
diff --git a/patches/patches/097_bit_manipulation.patch b/patches/patches/097_bit_manipulation.patch
index e216309..2afe3da 100644
--- a/patches/patches/097_bit_manipulation.patch
+++ b/patches/patches/097_bit_manipulation.patch
@@ -1,4 +1,4 @@
-82c82
+83c83
 <     ???;
 ---
 >     x ^= y;
diff --git a/patches/patches/098_bit_manipulation2.patch b/patches/patches/098_bit_manipulation2.patch
index 1b5df35..8becd34 100644
--- a/patches/patches/098_bit_manipulation2.patch
+++ b/patches/patches/098_bit_manipulation2.patch
@@ -1,4 +1,4 @@
-62c62
+63c63
 <     return bits == 0x..???;
 ---
 >     return bits == 0x3ffffff;
diff --git a/tools/check-exercises.py b/tools/check-exercises.py
new file mode 100755
index 0000000..fa0b5cb
--- /dev/null
+++ b/tools/check-exercises.py
@@ -0,0 +1,97 @@
+#!/usr/bin/env python
+
+import difflib
+import io
+import os
+import os.path
+import subprocess
+import sys
+
+
+IGNORE = subprocess.DEVNULL
+PIPE = subprocess.PIPE
+
+EXERCISES_PATH = "exercises"
+HEALED_PATH = "patches/healed"
+PATCHES_PATH = "patches/patches"
+
+
+# Heals all the exercises.
+def heal():
+    maketree(HEALED_PATH)
+
+    with os.scandir(EXERCISES_PATH) as it:
+        for entry in it:
+            name = entry.name
+
+            original_path = entry.path
+            patch_path = os.path.join(PATCHES_PATH, patch_name(name))
+            output_path = os.path.join(HEALED_PATH, name)
+
+            patch(original_path, patch_path, output_path)
+
+
+# Yields all the healed exercises that are not correctly formatted.
+def check_healed():
+    term = subprocess.run(
+        ["zig", "fmt", "--check", HEALED_PATH], stdout=PIPE, text=True
+    )
+    if term.stdout == "" and term.returncode != 0:
+        term.check_returncode()
+
+    stream = io.StringIO(term.stdout)
+    for line in stream:
+        yield line.strip()
+
+
+def main():
+    heal()
+
+    # Show the unified diff between the original example and the correctly
+    # formatted one.
+    for i, original in enumerate(check_healed()):
+        if i > 0:
+            print()
+
+        name = os.path.basename(original)
+        print(f"checking exercise {name}...\n")
+
+        from_file = open(original)
+        to_file = zig_fmt_file(original)
+
+        diff = difflib.unified_diff(
+            from_file.readlines(), to_file.readlines(), name, name + "-fmt"
+        )
+        sys.stderr.writelines(diff)
+
+
+def maketree(path):
+    return os.makedirs(path, exist_ok=True)
+
+
+# Returns path with the patch extension.
+def patch_name(path):
+    name, _ = os.path.splitext(path)
+
+    return name + ".patch"
+
+
+# Applies patch to original, and write the file to output.
+def patch(original, patch, output):
+    subprocess.run(
+        ["patch", "-i", patch, "-o", output, original], stdout=IGNORE, check=True
+    )
+
+
+# Formats the Zig file at path, and returns the possibly reformatted file as a
+# file object.
+def zig_fmt_file(path):
+    with open(path) as stdin:
+        term = subprocess.run(
+            ["zig", "fmt", "--stdin"], stdin=stdin, stdout=PIPE, check=True, text=True
+        )
+
+        return io.StringIO(term.stdout)
+
+
+main()
diff --git a/tools/update-patches.py b/tools/update-patches.py
new file mode 100755
index 0000000..76a1c46
--- /dev/null
+++ b/tools/update-patches.py
@@ -0,0 +1,68 @@
+#!/usr/bin/env python
+
+import os
+import os.path
+import subprocess
+
+
+IGNORE = subprocess.DEVNULL
+
+EXERCISES_PATH = "exercises"
+ANSWERS_PATH = "answers"
+PATCHES_PATH = "patches/patches"
+
+
+# Heals all the exercises.
+def heal():
+    maketree(ANSWERS_PATH)
+
+    with os.scandir(EXERCISES_PATH) as it:
+        for entry in it:
+            name = entry.name
+
+            original_path = entry.path
+            patch_path = os.path.join(PATCHES_PATH, patch_name(name))
+            output_path = os.path.join(ANSWERS_PATH, name)
+
+            patch(original_path, patch_path, output_path)
+
+
+def main():
+    heal()
+
+    with os.scandir(EXERCISES_PATH) as it:
+        for entry in it:
+            name = entry.name
+
+            broken_path = entry.path
+            healed_path = os.path.join(ANSWERS_PATH, name)
+            patch_path = os.path.join(PATCHES_PATH, patch_name(name))
+
+            with open(patch_path, "w") as file:
+                term = subprocess.run(
+                    ["diff", broken_path, healed_path],
+                    stdout=file,
+                    text=True,
+                )
+                assert term.returncode == 1
+
+
+def maketree(path):
+    return os.makedirs(path, exist_ok=True)
+
+
+# Returns path with the patch extension.
+def patch_name(path):
+    name, _ = os.path.splitext(path)
+
+    return name + ".patch"
+
+
+# Applies patch to original, and write the file to output.
+def patch(original, patch, output):
+    subprocess.run(
+        ["patch", "-i", patch, "-o", output, original], stdout=IGNORE, check=True
+    )
+
+
+main()