diff --git a/src/main.rs b/src/main.rs
index 53bf7af..9172ff3 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,5 +1,40 @@
+use std::time::Duration;
+
+use clap::Parser;
 use egui::Vec2;
-use katabastird::timer::Timer;
+use katabastird::timer::{CountDirection, Timer};
+
+#[derive(Debug, Parser)]
+#[clap(author, version, about)]
+struct Cli {
+    /// Hours to count down.
+    #[clap(long, default_value_t = 0)]
+    hours: u64,
+
+    /// Minutes to count down.
+    #[clap(long, short, default_value_t = 0)]
+    minutes: u64,
+
+    /// Seconds to count down.
+    #[clap(long, short, default_value_t = 0)]
+    seconds: u64,
+
+    /// Audio file to play at the end of the countdown.
+    #[clap(long, short)]
+    alarm: Option<String>,
+
+    /// Begin countdown immediately.
+    #[clap(long = "immediate", long = "running", short = 'i', short = 'r')]
+    running: bool,
+
+    /// Count up from zero, actually.
+    #[clap(long, short = 'u')]
+    count_up: bool,
+
+    /// Use the Predator font.
+    #[clap(long, short)]
+    predator: bool,
+}
 
 fn main() {
     let options = eframe::NativeOptions {
@@ -8,9 +43,20 @@ fn main() {
         ..Default::default()
     };
 
+    let cli = Cli::parse();
+
+    let seconds = cli.hours * 3600 + cli.minutes * 60 + cli.seconds;
+    let duration = Duration::from_secs(seconds.max(30));
+
+    let direction = if cli.count_up {
+        CountDirection::Up
+    } else {
+        CountDirection::Down
+    };
+
     eframe::run_native(
         "katabastird",
         options,
-        Box::new(|_cc| Box::new(Timer::default())),
+        Box::new(move |_cc| Box::new(Timer::new(duration, direction, !cli.running))),
     );
 }