diff --git a/13/build.zig b/13/build.zig
new file mode 100644
index 0000000..49143e1
--- /dev/null
+++ b/13/build.zig
@@ -0,0 +1,67 @@
+const std = @import("std");
+
+// Although this function looks imperative, note that its job is to
+// declaratively construct a build graph that will be executed by an external
+// runner.
+pub fn build(b: *std.Build) void {
+    // Standard target options allows the person running `zig build` to choose
+    // what target to build for. Here we do not override the defaults, which
+    // means any target is allowed, and the default is native. Other options
+    // for restricting supported target set are available.
+    const target = b.standardTargetOptions(.{});
+
+    // Standard optimization options allow the person running `zig build` to select
+    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
+    // set a preferred release mode, allowing the user to decide how to optimize.
+    const optimize = b.standardOptimizeOption(.{});
+
+    const exe = b.addExecutable(.{
+        .name = "13",
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    // 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);
+
+    // 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);
+
+    // 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());
+
+    // 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);
+    }
+
+    // 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);
+
+    const exe_unit_tests = b.addTest(.{
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    const run_exe_unit_tests = b.addRunArtifact(exe_unit_tests);
+    run_exe_unit_tests.has_side_effects = true;
+
+    // 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_exe_unit_tests.step);
+}
diff --git a/13/build.zig.zon b/13/build.zig.zon
new file mode 100644
index 0000000..390c9ff
--- /dev/null
+++ b/13/build.zig.zon
@@ -0,0 +1,72 @@
+.{
+    // This is the default name used by packages depending on this one. For
+    // example, when a user runs `zig fetch --save <url>`, this field is used
+    // as the key in the `dependencies` table. Although the user can choose a
+    // different name, most users will stick with this provided value.
+    //
+    // It is redundant to include "zig" in this name because it is already
+    // within the Zig package namespace.
+    .name = "13",
+
+    // This is a [Semantic Version](https://semver.org/).
+    // In a future version of Zig it will be used for package deduplication.
+    .version = "0.0.0",
+
+    // This field is optional.
+    // This is currently advisory only; Zig does not yet do anything
+    // with this value.
+    //.minimum_zig_version = "0.11.0",
+
+    // This field is optional.
+    // Each dependency must either provide a `url` and `hash`, or a `path`.
+    // `zig build --fetch` can be used to fetch all dependencies of a package, recursively.
+    // Once all dependencies are fetched, `zig build` no longer requires
+    // internet connectivity.
+    .dependencies = .{
+        // See `zig fetch --save <url>` for a command-line interface for adding dependencies.
+        //.example = .{
+        //    // When updating this field to a new URL, be sure to delete the corresponding
+        //    // `hash`, otherwise you are communicating that you expect to find the old hash at
+        //    // the new URL.
+        //    .url = "https://example.com/foo.tar.gz",
+        //
+        //    // This is computed from the file contents of the directory of files that is
+        //    // obtained after fetching `url` and applying the inclusion rules given by
+        //    // `paths`.
+        //    //
+        //    // This field is the source of truth; packages do not come from a `url`; they
+        //    // come from a `hash`. `url` is just one of many possible mirrors for how to
+        //    // obtain a package matching this `hash`.
+        //    //
+        //    // Uses the [multihash](https://multiformats.io/multihash/) format.
+        //    .hash = "...",
+        //
+        //    // When this is provided, the package is found in a directory relative to the
+        //    // build root. In this case the package's hash is irrelevant and therefore not
+        //    // computed. This field and `url` are mutually exclusive.
+        //    .path = "foo",
+
+        //    // When this is set to `true`, a package is declared to be lazily
+        //    // fetched. This makes the dependency only get fetched if it is
+        //    // actually used.
+        //    .lazy = false,
+        //},
+    },
+
+    // Specifies the set of files and directories that are included in this package.
+    // Only files and directories listed here are included in the `hash` that
+    // is computed for this package. Only files listed here will remain on disk
+    // when using the zig package manager. As a rule of thumb, one should list
+    // files required for compilation plus any license(s).
+    // Paths are relative to the build root. Use the empty string (`""`) to refer to
+    // the build root itself.
+    // A directory listed here means that all files within, recursively, are included.
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+        // For example...
+        //"LICENSE",
+        //"README.md",
+    },
+}
diff --git a/13/src/main.zig b/13/src/main.zig
new file mode 100644
index 0000000..2fbb66d
--- /dev/null
+++ b/13/src/main.zig
@@ -0,0 +1,161 @@
+// i hate math
+
+const std = @import("std");
+
+var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+const alloc = arena.allocator();
+
+const test_data = @embedFile("test");
+const input_data = @embedFile("input");
+
+pub fn main() !void {
+    const stdout = std.io.getStdOut().writer();
+
+    const value1 = try run1(input_data);
+    try stdout.print("{d}\n", .{value1});
+
+    const value2 = try run2(input_data);
+    try stdout.print("{d}\n", .{value2});
+}
+
+test "test input part 1" {
+    std.debug.print("\n", .{});
+    const value = try run1(test_data);
+    std.debug.print("{d}\n", .{value});
+    try std.testing.expectEqual(480, value);
+}
+
+test "test input part 2" {
+    std.debug.print("\n",.{});
+    const value = try run2(test_data);
+    std.debug.print("{d}\n", .{value});
+    try std.testing.expectEqual(0, value);
+}
+
+fn parseIntFromReader(reader: anytype) anyerror!u64 {
+    const f = try reader.readByte();
+    if (f < '0' or f > '9') return error.BadCharacter;
+    var v: u64 = f - '0';
+    while (true) {
+        const c = try reader.readByte();
+        if (c < '0' or c > '9') {
+            break;
+        } else {
+            v = (v * 10) + (c - '0');
+        }
+    }
+    return v;
+}
+
+// had some ideas but.
+// i hate math.
+// cheated. thx plasma ily :3 
+fn solve(a:f64,b:f64,c:f64,d:f64,e:f64,f:f64) [2]f64 {
+    const y = ((a*f)-(c*d))/(a*e-b*d);
+    const x = (c-b*y)/a;
+    return .{x,y};
+}
+
+fn run2(input: []const u8) !u64 {
+    const STATES = enum { A, B, G };
+    var state = STATES.A;
+    var lines = std.mem.splitScalar(u8, input, '\n');
+    var total: u64 = 0;
+
+    var ax: u64 = undefined;
+    var ay: u64 = undefined;
+    var bx: u64 = undefined;
+    var by: u64 = undefined;
+    while (lines.next()) |line| {
+        if (line.len == 0) continue;
+        var i: usize = 0;
+        while (line[i] < '0' or line[i] > '9') : (i += 1) {}
+        const x_s: usize = i;
+        while (line[i] >= '0' and line[i] <= '9') : (i += 1) {}
+        const x_e: usize = i;
+        while (line[i] < '0' or line[i] > '9') : (i += 1) {}
+        const y_s: usize = i;
+        while (i < line.len and line[i] >= '0' and line[i] <= '9') : (i += 1) {}
+        const y_e: usize = i;
+        var x = try std.fmt.parseInt(u64, line[x_s..x_e], 10);
+        var y = try std.fmt.parseInt(u64, line[y_s..y_e], 10);
+
+        switch (state) {
+            STATES.A => { ax = x; ay = y; state = STATES.B; },
+            STATES.B => { bx = x; by = y; state = STATES.G; },
+            STATES.G => {
+                x += 10000000000000;
+                y += 10000000000000;
+                const a: f64 = @floatFromInt(ax);
+                const d: f64 = @floatFromInt(ay);
+                const b: f64 = @floatFromInt(bx);
+                const e: f64 = @floatFromInt(by);
+                const c: f64 = @floatFromInt(x);
+                const f: f64 = @floatFromInt(y);
+                const r = solve(a,b,c,d,e,f);
+                const xi: u64 = @intFromFloat(r[0]);
+                const yi: u64 = @intFromFloat(r[1]);
+                const xm: f64 = @floatFromInt(xi);
+                const ym: f64 = @floatFromInt(yi);
+                if (xm-r[0] == 0 and ym-r[1] == 0) {
+                    total += xi*3 + yi;
+                }
+                state = STATES.A;
+            }
+        }
+    }
+
+    total += 0;
+    return total;
+}
+
+fn run1(input: []const u8) !u64 {
+    const STATES = enum { A, B, G };
+    var state = STATES.A;
+    var lines = std.mem.splitScalar(u8, input, '\n');
+    var total: u64 = 0;
+
+    var ax: u64 = undefined;
+    var ay: u64 = undefined;
+    var bx: u64 = undefined;
+    var by: u64 = undefined;
+    while (lines.next()) |line| {
+        if (line.len == 0) continue;
+        var i: usize = 0;
+        while (line[i] < '0' or line[i] > '9') : (i += 1) {}
+        const x_s: usize = i;
+        while (line[i] >= '0' and line[i] <= '9') : (i += 1) {}
+        const x_e: usize = i;
+        while (line[i] < '0' or line[i] > '9') : (i += 1) {}
+        const y_s: usize = i;
+        while (i < line.len and line[i] >= '0' and line[i] <= '9') : (i += 1) {}
+        const y_e: usize = i;
+        const x = try std.fmt.parseInt(u64, line[x_s..x_e], 10);
+        const y = try std.fmt.parseInt(u64, line[y_s..y_e], 10);
+
+        switch (state) {
+            STATES.A => { ax = x; ay = y; state = STATES.B; },
+            STATES.B => { bx = x; by = y; state = STATES.G; },
+            STATES.G => {
+                // find smallest solution
+                var bp: u64 = 1;
+                var ap: u64 = 0;
+                find: {
+                    while ((ax*ap + bx*bp) != x or (ay*ap + by*bp) != y) {
+                        bp += 1;
+                        if (bp == 100) {
+                            if (ap == 100) break :find;
+                            bp = 0;
+                            ap += 1;
+                        }
+                    }
+                    total += bp + ap*3;
+                }
+
+                state = STATES.A;
+            }
+        }
+    }
+
+    return total;
+}