diff --git a/hook.zsh b/hook.zsh
new file mode 100644
index 0000000..2dc77f5
--- /dev/null
+++ b/hook.zsh
@@ -0,0 +1,8 @@
+setopt promptsubst
+
+prompt_precmd() {
+  export PS1=`prim --ps1 --col $COLUMNS --row $LINES`
+  export RPS1=`prim --rps1 --col $COLUMNS --row $LINES`
+}
+
+add-zsh-hook precmd prompt_precmd
diff --git a/prim b/prim
new file mode 100755
index 0000000..5642bc4
Binary files /dev/null and b/prim differ
diff --git a/source/app.d b/source/app.d
index c3eec7f..25bb8e9 100644
--- a/source/app.d
+++ b/source/app.d
@@ -1,6 +1,42 @@
 import std.stdio;
+import std.getopt;
 
-void main()
-{
-	writeln("Edit source/app.d to start your project.");
+import prompt.ps1;
+
+struct Opt {
+  bool ps1;
+  bool rps1;
+
+  int col;
+  int row;
+}
+
+void validate(Opt opts) {
+  if (!opts.col || !opts.row)
+    throw new Exception("--col and --row required");
+}
+
+void main(string[] argv) {
+  Opt opts;
+
+  GetoptResult args = getopt(
+    argv,
+    std.getopt.config.bundling,
+    "ps1|p", "print PS1", &opts.ps1,
+    "rps1|r", "print RPS1", &opts.rps1,
+    "col", "terminal width", &opts.col,
+    "row", "terminal height", &opts.row,
+  );
+
+  if (args.helpWanted) {
+    defaultGetoptPrinter("prim", args.options);
+  }
+
+  try {
+    validate(opts);
+  } catch (Exception e) {
+    defaultGetoptPrinter(e.msg ~ "\n", args.options);
+  }
+
+  ps1(opts.col).write();
 }
diff --git a/source/prompt/ps1.d b/source/prompt/ps1.d
new file mode 100644
index 0000000..338afe8
--- /dev/null
+++ b/source/prompt/ps1.d
@@ -0,0 +1,11 @@
+module prompt.ps1;
+
+string ps1(int col) {
+  string ps;
+
+  foreach (i; 0 .. col) {
+    ps ~= '—';
+  }
+
+  return ps;
+}