diff --git a/Cargo.lock b/Cargo.lock
index 0152a7a..1c1d475 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,6 +2,717 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "anyhow"
+version = "1.0.71"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c7d0618f0e0b7e8ff11427422b64564d5fb0be1940354bfe2e0529b18a9d9b8"
+
+[[package]]
+name = "autocfg"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
+
+[[package]]
+name = "bitflags"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
+
+[[package]]
+name = "cairo-rs"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "bitflags",
+ "cairo-sys-rs",
+ "glib",
+ "libc",
+ "once_cell",
+ "thiserror",
+]
+
+[[package]]
+name = "cairo-sys-rs"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "glib-sys",
+ "libc",
+ "system-deps",
+]
+
+[[package]]
+name = "cfg-expr"
+version = "0.15.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "215c0072ecc28f92eeb0eea38ba63ddfcb65c2828c46311d646f1a3ff5f9841c"
+dependencies = [
+ "smallvec",
+ "target-lexicon",
+]
+
+[[package]]
+name = "equivalent"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "88bffebc5d80432c9b140ee17875ff173a8ab62faad5b257da912bd2f6c1c0a1"
+
+[[package]]
+name = "field-offset"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "38e2275cc4e4fc009b0669731a1e5ab7ebf11f469eaede2bab9309a5b4d6057f"
+dependencies = [
+ "memoffset",
+ "rustc_version",
+]
+
+[[package]]
+name = "futures-channel"
+version = "0.3.28"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "955518d47e09b25bbebc7a18df10b81f0c766eaf4c4f1cccef2fca5f2a4fb5f2"
+dependencies = [
+ "futures-core",
+]
+
+[[package]]
+name = "futures-core"
+version = "0.3.28"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4bca583b7e26f571124fe5b7561d49cb2868d79116cfa0eefce955557c6fee8c"
+
+[[package]]
+name = "futures-executor"
+version = "0.3.28"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ccecee823288125bd88b4d7f565c9e58e41858e47ab72e8ea2d64e93624386e0"
+dependencies = [
+ "futures-core",
+ "futures-task",
+ "futures-util",
+]
+
+[[package]]
+name = "futures-io"
+version = "0.3.28"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4fff74096e71ed47f8e023204cfd0aa1289cd54ae5430a9523be060cdb849964"
+
+[[package]]
+name = "futures-macro"
+version = "0.3.28"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "89ca545a94061b6365f2c7355b4b32bd20df3ff95f02da9329b34ccc3bd6ee72"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.22",
+]
+
+[[package]]
+name = "futures-task"
+version = "0.3.28"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76d3d132be6c0e6aa1534069c705a74a5997a356c0dc2f86a47765e5617c5b65"
+
+[[package]]
+name = "futures-util"
+version = "0.3.28"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "26b01e40b772d54cf6c6d721c1d1abd0647a0106a12ecaa1c186273392a69533"
+dependencies = [
+ "futures-core",
+ "futures-macro",
+ "futures-task",
+ "pin-project-lite",
+ "pin-utils",
+ "slab",
+]
+
+[[package]]
+name = "gdk-pixbuf"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "bitflags",
+ "gdk-pixbuf-sys",
+ "gio",
+ "glib",
+ "libc",
+ "once_cell",
+]
+
+[[package]]
+name = "gdk-pixbuf-sys"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "gio-sys",
+ "glib-sys",
+ "gobject-sys",
+ "libc",
+ "system-deps",
+]
+
+[[package]]
+name = "gdk4"
+version = "0.7.0"
+source = "git+https://github.com/gtk-rs/gtk4-rs.git#d5c2a897ae8ceb1e47a2d70d81ee9af8e63e0c98"
+dependencies = [
+ "bitflags",
+ "cairo-rs",
+ "gdk-pixbuf",
+ "gdk4-sys",
+ "gio",
+ "glib",
+ "libc",
+ "pango",
+]
+
+[[package]]
+name = "gdk4-sys"
+version = "0.7.0"
+source = "git+https://github.com/gtk-rs/gtk4-rs.git#d5c2a897ae8ceb1e47a2d70d81ee9af8e63e0c98"
+dependencies = [
+ "cairo-sys-rs",
+ "gdk-pixbuf-sys",
+ "gio-sys",
+ "glib-sys",
+ "gobject-sys",
+ "libc",
+ "pango-sys",
+ "pkg-config",
+ "system-deps",
+]
+
+[[package]]
+name = "gio"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "bitflags",
+ "futures-channel",
+ "futures-core",
+ "futures-io",
+ "futures-util",
+ "gio-sys",
+ "glib",
+ "libc",
+ "once_cell",
+ "pin-project-lite",
+ "smallvec",
+ "thiserror",
+]
+
+[[package]]
+name = "gio-sys"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "glib-sys",
+ "gobject-sys",
+ "libc",
+ "system-deps",
+ "winapi",
+]
+
+[[package]]
+name = "glib"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "bitflags",
+ "futures-channel",
+ "futures-core",
+ "futures-executor",
+ "futures-task",
+ "futures-util",
+ "gio-sys",
+ "glib-macros",
+ "glib-sys",
+ "gobject-sys",
+ "libc",
+ "memchr",
+ "once_cell",
+ "smallvec",
+ "thiserror",
+]
+
+[[package]]
+name = "glib-macros"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "anyhow",
+ "heck",
+ "proc-macro-crate",
+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.22",
+]
+
+[[package]]
+name = "glib-sys"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "libc",
+ "system-deps",
+]
+
+[[package]]
+name = "gobject-sys"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "glib-sys",
+ "libc",
+ "system-deps",
+]
+
+[[package]]
+name = "graphene-rs"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "glib",
+ "graphene-sys",
+ "libc",
+]
+
+[[package]]
+name = "graphene-sys"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "glib-sys",
+ "libc",
+ "pkg-config",
+ "system-deps",
+]
+
+[[package]]
+name = "gsk4"
+version = "0.7.0"
+source = "git+https://github.com/gtk-rs/gtk4-rs.git#d5c2a897ae8ceb1e47a2d70d81ee9af8e63e0c98"
+dependencies = [
+ "bitflags",
+ "cairo-rs",
+ "gdk4",
+ "glib",
+ "graphene-rs",
+ "gsk4-sys",
+ "libc",
+ "pango",
+]
+
+[[package]]
+name = "gsk4-sys"
+version = "0.7.0"
+source = "git+https://github.com/gtk-rs/gtk4-rs.git#d5c2a897ae8ceb1e47a2d70d81ee9af8e63e0c98"
+dependencies = [
+ "cairo-sys-rs",
+ "gdk4-sys",
+ "glib-sys",
+ "gobject-sys",
+ "graphene-sys",
+ "libc",
+ "pango-sys",
+ "system-deps",
+]
+
+[[package]]
+name = "gtk4"
+version = "0.7.0"
+source = "git+https://github.com/gtk-rs/gtk4-rs.git#d5c2a897ae8ceb1e47a2d70d81ee9af8e63e0c98"
+dependencies = [
+ "bitflags",
+ "cairo-rs",
+ "field-offset",
+ "futures-channel",
+ "gdk-pixbuf",
+ "gdk4",
+ "gio",
+ "glib",
+ "graphene-rs",
+ "gsk4",
+ "gtk4-macros",
+ "gtk4-sys",
+ "libc",
+ "once_cell",
+ "pango",
+]
+
+[[package]]
+name = "gtk4-macros"
+version = "0.7.0"
+source = "git+https://github.com/gtk-rs/gtk4-rs.git#d5c2a897ae8ceb1e47a2d70d81ee9af8e63e0c98"
+dependencies = [
+ "anyhow",
+ "proc-macro-crate",
+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn 1.0.109",
+]
+
+[[package]]
+name = "gtk4-sys"
+version = "0.7.0"
+source = "git+https://github.com/gtk-rs/gtk4-rs.git#d5c2a897ae8ceb1e47a2d70d81ee9af8e63e0c98"
+dependencies = [
+ "cairo-sys-rs",
+ "gdk-pixbuf-sys",
+ "gdk4-sys",
+ "gio-sys",
+ "glib-sys",
+ "gobject-sys",
+ "graphene-sys",
+ "gsk4-sys",
+ "libc",
+ "pango-sys",
+ "system-deps",
+]
+
+[[package]]
+name = "hashbrown"
+version = "0.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2c6201b9ff9fd90a5a3bac2e56a830d0caa509576f0e503818ee82c181b3437a"
+
+[[package]]
+name = "heck"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "95505c38b4572b2d910cecb0281560f54b440a19336cbbcb27bf6ce6adc6f5a8"
+
+[[package]]
+name = "indexmap"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d5477fe2230a79769d8dc68e0eabf5437907c0457a5614a9e8dddb67f65eb65d"
+dependencies = [
+ "equivalent",
+ "hashbrown",
+]
+
+[[package]]
+name = "libc"
+version = "0.2.147"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b4668fb0ea861c1df094127ac5f1da3409a82116a4ba74fca2e58ef927159bb3"
+
+[[package]]
+name = "memchr"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
+
+[[package]]
+name = "memoffset"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a634b1c61a95585bd15607c6ab0c4e5b226e695ff2800ba0cdccddf208c406c"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
+name = "once_cell"
+version = "1.18.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dd8b5dd2ae5ed71462c540258bedcb51965123ad7e7ccf4b9a8cafaa4a63576d"
+
+[[package]]
+name = "pango"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "bitflags",
+ "gio",
+ "glib",
+ "libc",
+ "once_cell",
+ "pango-sys",
+]
+
+[[package]]
+name = "pango-sys"
+version = "0.18.0"
+source = "git+https://github.com/gtk-rs/gtk-rs-core#ce523803aee59512d12af62d1ccbb281dceac880"
+dependencies = [
+ "glib-sys",
+ "gobject-sys",
+ "libc",
+ "system-deps",
+]
+
+[[package]]
+name = "pin-project-lite"
+version = "0.2.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e0a7ae3ac2f1173085d398531c705756c94a4c56843785df85a60c1a0afac116"
+
+[[package]]
+name = "pin-utils"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
+
+[[package]]
+name = "pkg-config"
+version = "0.3.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "26072860ba924cbfa98ea39c8c19b4dd6a4a25423dbdf219c1eca91aa0cf6964"
+
+[[package]]
+name = "proc-macro-crate"
+version = "1.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7f4c021e1093a56626774e81216a4ce732a735e5bad4868a03f3ed65ca0c3919"
+dependencies = [
+ "once_cell",
+ "toml_edit",
+]
+
+[[package]]
+name = "proc-macro-error"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da25490ff9892aab3fcf7c36f08cfb902dd3e71ca0f9f9517bea02a73a5ce38c"
+dependencies = [
+ "proc-macro-error-attr",
+ "proc-macro2",
+ "quote",
+ "syn 1.0.109",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro-error-attr"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1be40180e52ecc98ad80b184934baf3d0d29f979574e439af5a55274b35f869"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.63"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7b368fba921b0dce7e60f5e04ec15e565b3303972b42bcfde1d0713b881959eb"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.28"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1b9ab9c7eadfd8df19006f1cf1a4aed13540ed5cbc047010ece5826e10825488"
+dependencies = [
+ "proc-macro2",
+]
+
 [[package]]
 name = "rust-simple-gtk"
 version = "0.1.0"
+dependencies = [
+ "gtk4",
+]
+
+[[package]]
+name = "rustc_version"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bfa0f585226d2e68097d4f95d113b15b83a82e819ab25717ec0590d9584ef366"
+dependencies = [
+ "semver",
+]
+
+[[package]]
+name = "semver"
+version = "1.0.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bebd363326d05ec3e2f532ab7660680f3b02130d780c299bca73469d521bc0ed"
+
+[[package]]
+name = "serde"
+version = "1.0.164"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9e8c8cf938e98f769bc164923b06dce91cea1751522f46f8466461af04c9027d"
+
+[[package]]
+name = "serde_spanned"
+version = "0.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "96426c9936fd7a0124915f9185ea1d20aa9445cc9821142f0a73bc9207a2e186"
+dependencies = [
+ "serde",
+]
+
+[[package]]
+name = "slab"
+version = "0.4.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6528351c9bc8ab22353f9d776db39a20288e8d6c37ef8cfe3317cf875eecfc2d"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
+name = "smallvec"
+version = "1.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a507befe795404456341dfab10cef66ead4c041f62b8b11bbb92bffe5d0953e0"
+
+[[package]]
+name = "syn"
+version = "1.0.109"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72b64191b275b66ffe2469e8af2c1cfe3bafa67b529ead792a6d0160888b4237"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "syn"
+version = "2.0.22"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2efbeae7acf4eabd6bcdcbd11c92f45231ddda7539edc7806bd1a04a03b24616"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "system-deps"
+version = "6.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "30c2de8a4d8f4b823d634affc9cd2a74ec98c53a756f317e529a48046cbf71f3"
+dependencies = [
+ "cfg-expr",
+ "heck",
+ "pkg-config",
+ "toml",
+ "version-compare",
+]
+
+[[package]]
+name = "target-lexicon"
+version = "0.12.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1b1c7f239eb94671427157bd93b3694320f3668d4e1eff08c7285366fd777fac"
+
+[[package]]
+name = "thiserror"
+version = "1.0.40"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "978c9a314bd8dc99be594bc3c175faaa9794be04a5a5e153caba6915336cebac"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.40"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f9456a42c5b0d803c8cd86e73dd7cc9edd429499f37a3550d286d5e86720569f"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.22",
+]
+
+[[package]]
+name = "toml"
+version = "0.7.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1ebafdf5ad1220cb59e7d17cf4d2c72015297b75b19a10472f99b89225089240"
+dependencies = [
+ "serde",
+ "serde_spanned",
+ "toml_datetime",
+ "toml_edit",
+]
+
+[[package]]
+name = "toml_datetime"
+version = "0.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7cda73e2f1397b1262d6dfdcef8aafae14d1de7748d66822d3bfeeb6d03e5e4b"
+dependencies = [
+ "serde",
+]
+
+[[package]]
+name = "toml_edit"
+version = "0.19.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "266f016b7f039eec8a1a80dfe6156b633d208b9fccca5e4db1d6775b0c4e34a7"
+dependencies = [
+ "indexmap",
+ "serde",
+ "serde_spanned",
+ "toml_datetime",
+ "winnow",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b15811caf2415fb889178633e7724bad2509101cde276048e013b9def5e51fa0"
+
+[[package]]
+name = "version-compare"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "579a42fc0b8e0c63b76519a339be31bed574929511fa53c1a3acae26eb258f29"
+
+[[package]]
+name = "version_check"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
+
+[[package]]
+name = "winapi"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c839a674fcd7a98952e593242ea400abe93992746761e38641405d28b00f419"
+dependencies = [
+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
+
+[[package]]
+name = "winapi-i686-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
+
+[[package]]
+name = "winapi-x86_64-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
+
+[[package]]
+name = "winnow"
+version = "0.4.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ca0ace3845f0d96209f0375e6d367e3eb87eb65d27d445bdc9f1843a26f39448"
+dependencies = [
+ "memchr",
+]
diff --git a/Cargo.toml b/Cargo.toml
index ec34140..00e68d3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,3 +6,4 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+gtk = { git = "https://github.com/gtk-rs/gtk4-rs.git", package = "gtk4" }
diff --git a/src/main.rs b/src/main.rs
index 7da3a48..f28ca33 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,23 @@
+use gtk::{glib, prelude::*};
+use gtk::{Application, ApplicationWindow};
 
-fn main() {
-    println!("Hello, world!");
+fn main() -> glib::ExitCode {
+    let app = Application::builder()
+        .application_id("org.example.HelloWorld")
+        .build();
+
+    app.connect_activate(|app| {
+        // We create the main window.
+        let window = ApplicationWindow::builder()
+            .application(app)
+            .default_width(320)
+            .default_height(200)
+            .title("Hello, World!")
+            .build();
+
+        // Show the window.
+        window.show();
+    });
+
+    app.run()
 }