diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..20d5f35
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,10 @@
+version: 2
+updates:
+  - package-ecosystem: gomod
+    directory: "/"
+    schedule:
+      interval: daily
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: daily
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
new file mode 100644
index 0000000..49e2b0e
--- /dev/null
+++ b/.github/workflows/build.yml
@@ -0,0 +1,17 @@
+name: build
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  schedule:
+    - cron: '0 0 * * 0' # run "At 00:00 on Sunday"
+
+# See https://github.com/cristalhq/.github/.github/workflows
+jobs:
+  build:
+    uses: cristalhq/.github/.github/workflows/build.yml@v0.5.0
+
+  vuln:
+    uses: cristalhq/.github/.github/workflows/vuln.yml@v0.5.0
diff --git a/README.md b/README.md
index 58bfd46..bd7104c 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,42 @@
 # bson
-BSON for Go
+
+[![build-img]][build-url]
+[![pkg-img]][pkg-url]
+[![version-img]][version-url]
+
+BSON for Go.
+
+## Features
+
+* Simple API.
+* Dependency-free.
+* Clean and tested code.
+
+See [docs][pkg-url] for more details.
+
+## Install
+
+Go version 1.18+
+
+```
+go get github.com/cristalhq/bson
+```
+
+## Example
+
+```go
+TODO
+```
+
+See examples: [example_test.go](example_test.go).
+
+## License
+
+[MIT License](LICENSE).
+
+[build-img]: https://github.com/cristalhq/bson/workflows/build/badge.svg
+[build-url]: https://github.com/cristalhq/bson/actions
+[pkg-img]: https://pkg.go.dev/badge/cristalhq/bson
+[pkg-url]: https://pkg.go.dev/github.com/cristalhq/bson
+[version-img]: https://img.shields.io/github/v/release/cristalhq/bson
+[version-url]: https://github.com/cristalhq/bson/releases
diff --git a/bson.go b/bson.go
new file mode 100644
index 0000000..7663e02
--- /dev/null
+++ b/bson.go
@@ -0,0 +1,16 @@
+package bson
+
+// Marshaler is the interface implemented by types that
+// can marshal themselves into valid BSON.
+type Marshaler interface {
+	MarshalBSON() ([]byte, error)
+}
+
+// Unmarshaler is the interface implemented by types that
+// can unmarshal a BSON representation of themselves.
+//
+// The input can be assumed to be a valid encoding of a BSON.
+// UnmarshalBSON must copy the BSON data if it wishes to retain the data after returning.
+type Unmarshaler interface {
+	UnmarshalBSON([]byte) error
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..1aa38a8
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module bson
+
+go 1.18
diff --git a/type.go b/type.go
new file mode 100644
index 0000000..dd379da
--- /dev/null
+++ b/type.go
@@ -0,0 +1,29 @@
+package bson
+
+// Type represents a BSON type.
+type Type byte
+
+// BSON element types as described in https://bsonspec.org/spec.html.
+const (
+	TypeDouble          Type = 0x01
+	TypeString          Type = 0x02
+	TypeDocument        Type = 0x03
+	TypeArray           Type = 0x04
+	TypeBinary          Type = 0x05
+	TypeUndefined       Type = 0x06
+	TypeObjectID        Type = 0x07
+	TypeBool            Type = 0x08
+	TypeDateTime        Type = 0x09
+	TypeNull            Type = 0x0a
+	TypeRegex           Type = 0x0b
+	TypeDBPointer       Type = 0x0c
+	TypeCodeWithScope   Type = 0x0d
+	TypeSymbol          Type = 0x0e
+	TypeJavaScriptScope Type = 0x0f
+	TypeInt32           Type = 0x10
+	TypeTimestamp       Type = 0x11
+	TypeInt64           Type = 0x12
+	TypeDecimal         Type = 0x13
+	TypeMinKey          Type = 0xff
+	TypeMaxKey          Type = 0x7f
+)