diff --git a/exercises/001_hello.zig b/exercises/001_hello.zig
index 7f40b92..93a0cfb 100644
--- a/exercises/001_hello.zig
+++ b/exercises/001_hello.zig
@@ -16,6 +16,6 @@
 //
 const std = @import("std");
 
-fn main() void {
+pub fn main() void {
     std.debug.print("Hello world!\n", .{});
 }
diff --git a/exercises/002_std.zig b/exercises/002_std.zig
index 8cc3792..5916c7c 100644
--- a/exercises/002_std.zig
+++ b/exercises/002_std.zig
@@ -11,7 +11,7 @@
 // Please complete the import below:
 //
 
-??? = @import("std");
+const std = @import("std");
 
 pub fn main() void {
     std.debug.print("Standard Library.\n", .{});
diff --git a/exercises/003_assignment.zig b/exercises/003_assignment.zig
index 10ba8cb..ed05855 100644
--- a/exercises/003_assignment.zig
+++ b/exercises/003_assignment.zig
@@ -34,12 +34,12 @@
 const std = @import("std");
 
 pub fn main() void {
-    const n: u8 = 50;
+    var n: u16 = 50;
     n = n + 5;
 
-    const pi: u8 = 314159;
+    const pi: u32 = 314159;
 
-    const negative_eleven: u8 = -11;
+    const negative_eleven: i8 = -11;
 
     // There are no errors in the next line, just explanation:
     // Perhaps you noticed before that the print function takes two
diff --git a/exercises/004_arrays.zig b/exercises/004_arrays.zig
index 88fcc78..b6756bb 100644
--- a/exercises/004_arrays.zig
+++ b/exercises/004_arrays.zig
@@ -27,7 +27,7 @@ pub fn main() void {
     // (Problem 1)
     // This "const" is going to cause a problem later - can you see what it is?
     // How do we fix it?
-    const some_primes = [_]u8{ 1, 3, 5, 7, 11, 13, 17, 19 };
+    var some_primes = [_]u8{ 1, 3, 5, 7, 11, 13, 17, 19 };
 
     // Individual values can be set with '[]' notation.
     // Example: This line changes the first prime to 2 (which is correct):
@@ -40,11 +40,11 @@ pub fn main() void {
     // (Problem 2)
     // Looks like we need to complete this expression. Use the example
     // above to set "fourth" to the fourth element of the some_primes array:
-    const fourth = some_primes[???];
+    const fourth = some_primes[3];
 
     // (Problem 3)
     // Use the len property to get the length of the array:
-    const length = some_primes.???;
+    const length = some_primes.len;
 
     std.debug.print("First: {}, Fourth: {}, Length: {}\n", .{
         first, fourth, length,
diff --git a/exercises/005_arrays2.zig b/exercises/005_arrays2.zig
index 07b9abe..e170266 100644
--- a/exercises/005_arrays2.zig
+++ b/exercises/005_arrays2.zig
@@ -21,12 +21,12 @@ pub fn main() void {
     // (Problem 1)
     // Please set this array concatenating the two arrays above.
     // It should result in: 1 3 3 7
-    const leet = ???;
+    const leet = le ++ et;
 
     // (Problem 2)
     // Please set this array using repetition.
     // It should result in: 1 0 0 1 1 0 0 1 1 0 0 1
-    const bit_pattern_unit = [_]u8{ ??? };
+    const bit_pattern_unit = [_]u8{ 1, 0, 0, 1 };
     const bit_pattern: [3 * bit_pattern_unit.len]u8 = @bitCast(@as([3][bit_pattern_unit.len]u8, @splat(bit_pattern_unit)));
 
     // Okay, that's all of the problems. Let's see the results.
diff --git a/exercises/006_strings.zig b/exercises/006_strings.zig
index 08977de..eb3a8f6 100644
--- a/exercises/006_strings.zig
+++ b/exercises/006_strings.zig
@@ -24,14 +24,14 @@ pub fn main() void {
     // (Problem 1)
     // Use array square bracket syntax to get the letter 'd' from
     // the string "stardust" above.
-    const d: u8 = ziggy[???];
+    const d: u8 = ziggy[4];
 
     // (Problem 2)
     // Use the array concatenation '++' operator to make "Major Tom".
     // (You'll need to add a space as well!)
     const major = "Major";
     const tom = "Tom";
-    const major_tom = major ??? tom;
+    const major_tom = major ++ " " ++ tom;
 
     // That's all the problems. Let's see our results:
     std.debug.print("d={u} {s}\n", .{ d, major_tom });
diff --git a/exercises/007_strings2.zig b/exercises/007_strings2.zig
index 6350be1..74cb752 100644
--- a/exercises/007_strings2.zig
+++ b/exercises/007_strings2.zig
@@ -15,9 +15,9 @@ const std = @import("std");
 
 pub fn main() void {
     const lyrics =
-        Ziggy played guitar
-        Jamming good with Andrew Kelley
-        And the Spiders from Mars
+        \\Ziggy played guitar
+        \\Jamming good with Andrew Kelley
+        \\And the Spiders from Mars
     ;
 
     std.debug.print("{s}\n", .{lyrics});
diff --git a/exercises/008_quiz.zig b/exercises/008_quiz.zig
index 5a81fb2..dff4da3 100644
--- a/exercises/008_quiz.zig
+++ b/exercises/008_quiz.zig
@@ -19,7 +19,7 @@ pub fn main() void {
     // the idiomatic type to use for array indexing.
     //
     // There IS a problem on this line, but 'usize' isn't it.
-    const x: usize = 1;
+    var x: usize = 1;
 
     // Note: When you want to declare memory (an array in this
     // case) without putting anything in it, you can set it to
@@ -33,10 +33,10 @@ pub fn main() void {
     lang[0] = letters[x];
 
     x = 3;
-    lang[???] = letters[x];
+    lang[1] = letters[x];
 
-    x = ???;
-    lang[2] = letters[???];
+    x = 5;
+    lang[2] = letters[x];
 
     // We want to "Program in Zig!" of course:
     std.debug.print("Program in {s}!\n", .{lang});
diff --git a/exercises/009_if.zig b/exercises/009_if.zig
index e167104..68bf04b 100644
--- a/exercises/009_if.zig
+++ b/exercises/009_if.zig
@@ -24,7 +24,7 @@ pub fn main() void {
     const foo = 42;
 
     // Please fix this condition:
-    if (foo) {
+    if (foo == 42) {
         // We want our program to print this message!
         std.debug.print("Foo is 42!\n", .{});
     } else {
diff --git a/exercises/010_if2.zig b/exercises/010_if2.zig
index f0ffb43..7bbc01c 100644
--- a/exercises/010_if2.zig
+++ b/exercises/010_if2.zig
@@ -10,7 +10,7 @@ pub fn main() void {
 
     // Please use an if...else expression to set "price".
     // If discount is true, the price should be $17, otherwise $20:
-    const price: u8 = if ???;
+    const price: u8 = if (discount) 17 else 20;
 
     std.debug.print("With the discount, the price is ${}.\n", .{price});
 }
diff --git a/exercises/011_while.zig b/exercises/011_while.zig
index 674d904..f04fcbe 100644
--- a/exercises/011_while.zig
+++ b/exercises/011_while.zig
@@ -21,7 +21,7 @@ pub fn main() void {
     var n: u32 = 2;
 
     // Please use a condition that is true UNTIL "n" reaches 1024:
-    while (???) {
+    while (n != 1024) {
         // Print the current number
         std.debug.print("{} ", .{n});
 
diff --git a/exercises/012_while2.zig b/exercises/012_while2.zig
index c9905aa..6f8e168 100644
--- a/exercises/012_while2.zig
+++ b/exercises/012_while2.zig
@@ -25,7 +25,7 @@ pub fn main() void {
 
     // Please set the continue expression so that we get the desired
     // results in the print statement below.
-    while (n < 1000) : ??? {
+    while (n < 1000) : (n *= 2) {
         // Print the current number
         std.debug.print("{} ", .{n});
     }
diff --git a/exercises/013_while3.zig b/exercises/013_while3.zig
index 52d5ebd..715a6d1 100644
--- a/exercises/013_while3.zig
+++ b/exercises/013_while3.zig
@@ -24,8 +24,8 @@ pub fn main() void {
     while (n <= 20) : (n += 1) {
         // The '%' symbol is the "modulo" operator and it
         // returns the remainder after division.
-        if (n % 3 == 0) ???;
-        if (n % 5 == 0) ???;
+        if (n % 3 == 0) continue;
+        if (n % 5 == 0) continue;
         std.debug.print("{} ", .{n});
     }
 
diff --git a/exercises/014_while4.zig b/exercises/014_while4.zig
index 95aecb0..dfd48fc 100644
--- a/exercises/014_while4.zig
+++ b/exercises/014_while4.zig
@@ -18,7 +18,7 @@ pub fn main() void {
     // Oh dear! This while loop will go forever?!
     // Please fix this so the print statement below gives the desired output.
     while (true) : (n += 1) {
-        if (???) ???;
+        if (n == 4) break;
     }
 
     // Result: we want n=4
diff --git a/exercises/015_for.zig b/exercises/015_for.zig
index 0ee8e7d..e6b9729 100644
--- a/exercises/015_for.zig
+++ b/exercises/015_for.zig
@@ -15,7 +15,7 @@ pub fn main() void {
 
     std.debug.print("A Dramatic Story: ", .{});
 
-    for (???) |???| {
+    for (story) |scene| {
         if (scene == 'h') std.debug.print(":-)  ", .{});
         if (scene == 's') std.debug.print(":-(  ", .{});
         if (scene == 'n') std.debug.print(":-|  ", .{});
diff --git a/exercises/016_for2.zig b/exercises/016_for2.zig
index 6fb7844..eaab65f 100644
--- a/exercises/016_for2.zig
+++ b/exercises/016_for2.zig
@@ -25,7 +25,7 @@ pub fn main() void {
     // the value of the place as a power of two for each bit.
     //
     // See if you can figure out the missing pieces:
-    for (bits, ???) |bit, ???| {
+    for (bits, 0..) |bit, i| {
         // Note that we convert the usize i to a u32 with
         // @intCast(), a builtin function just like @import().
         // We'll learn about these properly in a later exercise.
diff --git a/exercises/017_quiz2.zig b/exercises/017_quiz2.zig
index 6f32c2e..4ad3ca7 100644
--- a/exercises/017_quiz2.zig
+++ b/exercises/017_quiz2.zig
@@ -9,18 +9,18 @@
 // Let's go from 1 to 16. This has been started for you, but there
 // are some problems. :-(
 //
-const std = import standard library;
+const std = @import("std");
 
-function main() void {
+pub fn main() void {
     var i: u8 = 1;
     const stop_at: u8 = 16;
 
     // What kind of loop is this? A 'for' or a 'while'?
-    ??? (i <= stop_at) : (i += 1) {
+    while (i <= stop_at) : (i += 1) {
         if (i % 3 == 0) std.debug.print("Fizz", .{});
         if (i % 5 == 0) std.debug.print("Buzz", .{});
         if (!(i % 3 == 0) and !(i % 5 == 0)) {
-            std.debug.print("{}", .{???});
+            std.debug.print("{}", .{i});
         }
         std.debug.print(", ", .{});
     }
diff --git a/exercises/018_functions.zig b/exercises/018_functions.zig
index 1f78438..c9cc6c5 100644
--- a/exercises/018_functions.zig
+++ b/exercises/018_functions.zig
@@ -25,6 +25,6 @@ pub fn main() void {
 // We're just missing a couple things. One thing we're NOT missing is the
 // keyword "pub", which is not needed here. Can you guess why?
 //
-??? deepThought() ??? {
+fn deepThought() u8 {
     return 42; // Number courtesy Douglas Adams
 }
diff --git a/exercises/019_functions2.zig b/exercises/019_functions2.zig
index 5a76c7b..de90b87 100644
--- a/exercises/019_functions2.zig
+++ b/exercises/019_functions2.zig
@@ -22,7 +22,7 @@ pub fn main() void {
 // You'll need to figure out the parameter name and type that we're
 // expecting. The output type has already been specified for you.
 //
-fn twoToThe(???) u32 {
+fn twoToThe(my_number: u32) u32 {
     return std.math.pow(u32, 2, my_number);
     // std.math.pow(type, a, b) takes a numeric type and two
     // numbers of that type (or that can coerce to that type) and
diff --git a/exercises/020_quiz3.zig b/exercises/020_quiz3.zig
index 571628e..2284999 100644
--- a/exercises/020_quiz3.zig
+++ b/exercises/020_quiz3.zig
@@ -21,8 +21,8 @@ pub fn main() void {
 //
 // This function prints, but does not return anything.
 //
-fn printPowersOfTwo(numbers: [4]u16) ??? {
-    loop (numbers) |n| {
+fn printPowersOfTwo(numbers: [4]u16) void {
+    for (numbers) |n| {
         std.debug.print("{} ", .{twoToThe(n)});
     }
 }
@@ -31,13 +31,13 @@ fn printPowersOfTwo(numbers: [4]u16) ??? {
 // exercise. But don't be fooled! This one does the math without the aid
 // of the standard library!
 //
-fn twoToThe(number: u16) ??? {
+fn twoToThe(number: u16) u16 {
     var n: u16 = 0;
     var total: u16 = 1;
 
-    loop (n < number) : (n += 1) {
+    while (n < number) : (n += 1) {
         total *= 2;
     }
 
-    return ???;
+    return total;
 }
diff --git a/exercises/021_errors.zig b/exercises/021_errors.zig
index 7afeace..a6670b1 100644
--- a/exercises/021_errors.zig
+++ b/exercises/021_errors.zig
@@ -9,7 +9,7 @@
 // "TooSmall". Please add it where needed!
 const MyNumberError = error{
     TooBig,
-    ???,
+    TooSmall,
     TooFour,
 };
 
@@ -26,7 +26,7 @@ pub fn main() void {
         if (number_error == MyNumberError.TooBig) {
             std.debug.print(">4. ", .{});
         }
-        if (???) {
+        if (number_error == MyNumberError.TooSmall) {
             std.debug.print("<4. ", .{});
         }
         if (number_error == MyNumberError.TooFour) {
diff --git a/exercises/022_errors2.zig b/exercises/022_errors2.zig
index 1d513b3..0d4bb73 100644
--- a/exercises/022_errors2.zig
+++ b/exercises/022_errors2.zig
@@ -19,7 +19,7 @@ const std = @import("std");
 const MyNumberError = error{TooSmall};
 
 pub fn main() void {
-    var my_number: ??? = 5;
+    var my_number: MyNumberError!u8 = 5;
 
     // Looks like my_number will need to either store a number OR
     // an error. Can you set the type correctly above?
diff --git a/exercises/023_errors3.zig b/exercises/023_errors3.zig
index 195f21a..f538a2d 100644
--- a/exercises/023_errors3.zig
+++ b/exercises/023_errors3.zig
@@ -12,14 +12,14 @@ const MyNumberError = error{TooSmall};
 
 pub fn main() void {
     const a: u32 = addTwenty(44) catch 22;
-    const b: u32 = addTwenty(4) ??? 22;
+    const b: u32 = addTwenty(4) catch 22;
 
     std.debug.print("a={}, b={}\n", .{ a, b });
 }
 
 // Please provide the return type from this function.
 // Hint: it'll be an error union.
-fn addTwenty(n: u32) ??? {
+fn addTwenty(n: u32) !u32 {
     if (n < 5) {
         return MyNumberError.TooSmall;
     } else {