diff --git a/build.zig b/build.zig
index c7c73a4..eb0e2f5 100644
--- a/build.zig
+++ b/build.zig
@@ -15,56 +15,57 @@ pub fn build(b: *std.Build) void {
     // set a preferred release mode, allowing the user to decide how to optimize.
     const optimize = b.standardOptimizeOption(.{});
 
-    const exe = b.addExecutable(.{
-        .name = "aoc23",
-        // In this case the main source file is merely a path, however, in more
-        // complicated build scripts, this could be a generated file.
-        .root_source_file = .{ .path = "src/main.zig" },
-        .target = target,
-        .optimize = optimize,
-    });
+    // Build harness based on https://github.com/SpexGuy/Zig-AoC-Template.
 
-    // This declares intent for the executable to be installed into the
-    // standard location when the user invokes the "install" step (the default
-    // step when running `zig build`).
-    b.installArtifact(exe);
+    // Build, run, and install targets for "all."
+    const build_all = b.step("all", "Build all days");
+    const run_all = b.step("run", "Run all days");
+    const test_all = b.step("test", "Run all tests");
 
-    // This *creates* a Run step in the build graph, to be executed when another
-    // step is evaluated that depends on it. The next line below will establish
-    // such a dependency.
-    const run_cmd = b.addRunArtifact(exe);
+    // Generate build, run, and install targets for all days that have been
+    // created.
+    for (1..25) |day| {
+        const day_string = b.fmt("day{:0>2}", .{day});
+        const src = b.fmt("src/{s}.zig", .{day_string});
+        std.fs.cwd().access(src, .{}) catch continue;
 
-    // By making the run step depend on the install step, it will be run from the
-    // installation directory rather than directly from within the cache directory.
-    // This is not necessary, however, if the application depends on other installed
-    // files, this ensures they will be present and in the expected location.
-    run_cmd.step.dependOn(b.getInstallStep());
+        // Build and install
+        const exe = b.addExecutable(.{
+            .name = b.fmt("aoc23-{s}", .{day_string}),
+            .root_source_file = .{ .path = src },
+            .target = target,
+            .optimize = optimize,
+        });
+        b.installArtifact(exe);
+        build_all.dependOn(&exe.step);
 
-    // This allows the user to pass arguments to the application in the build
-    // command itself, like this: `zig build run -- arg1 arg2 etc`
-    if (b.args) |args| {
-        run_cmd.addArgs(args);
+        // Run
+        const run_cmd = b.addRunArtifact(exe);
+        run_cmd.step.dependOn(b.getInstallStep());
+        if (b.args) |args| {
+            run_cmd.addArgs(args);
+        }
+
+        const run_step = b.step(
+            b.fmt("run-{s}", .{day_string}),
+            b.fmt("Run {s} executable", .{day_string}),
+        );
+        run_step.dependOn(&run_cmd.step);
+        run_all.dependOn(&run_cmd.step);
+
+        // Test
+        const unit_test = b.addTest(.{
+            .root_source_file = .{ .path = src },
+            .target = target,
+            .optimize = optimize,
+        });
+
+        const test_cmd = b.addRunArtifact(unit_test);
+        const test_step = b.step(
+            b.fmt("test-{s}", .{day_string}),
+            b.fmt("Run {s} tests", .{day_string}),
+        );
+        test_step.dependOn(&test_cmd.step);
+        test_all.dependOn(&test_cmd.step);
     }
-
-    // This creates a build step. It will be visible in the `zig build --help` menu,
-    // and can be selected like this: `zig build run`
-    // This will evaluate the `run` step rather than the default, which is "install".
-    const run_step = b.step("run", "Run the app");
-    run_step.dependOn(&run_cmd.step);
-
-    // Creates a step for unit testing. This only builds the test executable
-    // but does not run it.
-    const unit_tests = b.addTest(.{
-        .root_source_file = .{ .path = "src/main.zig" },
-        .target = target,
-        .optimize = optimize,
-    });
-
-    const run_unit_tests = b.addRunArtifact(unit_tests);
-
-    // Similar to creating the run step earlier, this exposes a `test` step to
-    // the `zig build --help` menu, providing a way for the user to request
-    // running the unit tests.
-    const test_step = b.step("test", "Run unit tests");
-    test_step.dependOn(&run_unit_tests.step);
 }
diff --git a/src/day01.zig b/src/day01.zig
new file mode 100644
index 0000000..ff7c164
--- /dev/null
+++ b/src/day01.zig
@@ -0,0 +1,4 @@
+const std = @import("std");
+const util = @import("util.zig");
+
+pub fn main() !void {}
diff --git a/src/main.zig b/src/main.zig
deleted file mode 100644
index c8a3f67..0000000
--- a/src/main.zig
+++ /dev/null
@@ -1,24 +0,0 @@
-const std = @import("std");
-
-pub fn main() !void {
-    // Prints to stderr (it's a shortcut based on `std.io.getStdErr()`)
-    std.debug.print("All your {s} are belong to us.\n", .{"codebase"});
-
-    // stdout is for the actual output of your application, for example if you
-    // are implementing gzip, then only the compressed bytes should be sent to
-    // stdout, not any debugging messages.
-    const stdout_file = std.io.getStdOut().writer();
-    var bw = std.io.bufferedWriter(stdout_file);
-    const stdout = bw.writer();
-
-    try stdout.print("Run `zig build test` to run the tests.\n", .{});
-
-    try bw.flush(); // don't forget to flush!
-}
-
-test "simple test" {
-    var list = std.ArrayList(i32).init(std.testing.allocator);
-    defer list.deinit(); // try commenting this out and see if zig detects the memory leak!
-    try list.append(42);
-    try std.testing.expectEqual(@as(i32, 42), list.pop());
-}
diff --git a/src/util.zig b/src/util.zig
new file mode 100644
index 0000000..e6e4e05
--- /dev/null
+++ b/src/util.zig
@@ -0,0 +1,4 @@
+const std = @import("std");
+
+const gpa_impl = std.heap.GeneralPurposeAllocator(.{});
+pub const gpa = gpa_impl.allocator();