diff --git a/Cargo.lock b/Cargo.lock
index e89833e..9a82be0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -87,6 +87,16 @@ dependencies = [
  "os_str_bytes",
 ]
 
+[[package]]
+name = "ctrlc"
+version = "3.2.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bbcf33c2a618cbe41ee43ae6e9f2e48368cd9f9db2896f10167d8d762679f639"
+dependencies = [
+ "nix",
+ "windows-sys 0.45.0",
+]
+
 [[package]]
 name = "errno"
 version = "0.2.8"
@@ -177,7 +187,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "46112a93252b123d31a119a8d1a1ac19deac4fac6e0e8b0df58f0d4e5870e63c"
 dependencies = [
  "libc",
- "windows-sys",
+ "windows-sys 0.42.0",
 ]
 
 [[package]]
@@ -189,7 +199,7 @@ dependencies = [
  "hermit-abi",
  "io-lifetimes",
  "rustix",
- "windows-sys",
+ "windows-sys 0.42.0",
 ]
 
 [[package]]
@@ -256,6 +266,18 @@ dependencies = [
  "serde_json",
 ]
 
+[[package]]
+name = "nix"
+version = "0.26.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bfdda3d196821d6af13126e40375cdf7da646a96114af134d5f417a9a1dc8e1a"
+dependencies = [
+ "bitflags",
+ "cfg-if",
+ "libc",
+ "static_assertions",
+]
+
 [[package]]
 name = "nu-ansi-term"
 version = "0.46.0"
@@ -412,7 +434,7 @@ dependencies = [
  "io-lifetimes",
  "libc",
  "linux-raw-sys",
- "windows-sys",
+ "windows-sys 0.42.0",
 ]
 
 [[package]]
@@ -476,6 +498,12 @@ version = "1.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a507befe795404456341dfab10cef66ead4c041f62b8b11bbb92bffe5d0953e0"
 
+[[package]]
+name = "static_assertions"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a2eb9349b6444b326872e140eb1cf5e7c522154d69e7a0ffb0fb81c06b37543f"
+
 [[package]]
 name = "strsim"
 version = "0.10.0"
@@ -518,6 +546,7 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "clap",
+ "ctrlc",
  "fish",
  "mino",
  "rand",
@@ -696,46 +725,70 @@ dependencies = [
 ]
 
 [[package]]
-name = "windows_aarch64_gnullvm"
-version = "0.42.0"
+name = "windows-sys"
+version = "0.45.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "41d2aa71f6f0cbe00ae5167d90ef3cfe66527d6f613ca78ac8024c3ccab9a19e"
+checksum = "75283be5efb2831d37ea142365f009c02ec203cd29a3ebecbc093d52315b66d0"
+dependencies = [
+ "windows-targets",
+]
+
+[[package]]
+name = "windows-targets"
+version = "0.42.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8e5180c00cd44c9b1c88adb3693291f1cd93605ded80c250a75d472756b4d071"
+dependencies = [
+ "windows_aarch64_gnullvm",
+ "windows_aarch64_msvc",
+ "windows_i686_gnu",
+ "windows_i686_msvc",
+ "windows_x86_64_gnu",
+ "windows_x86_64_gnullvm",
+ "windows_x86_64_msvc",
+]
+
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.42.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "597a5118570b68bc08d8d59125332c54f1ba9d9adeedeef5b99b02ba2b0698f8"
 
 [[package]]
 name = "windows_aarch64_msvc"
-version = "0.42.0"
+version = "0.42.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dd0f252f5a35cac83d6311b2e795981f5ee6e67eb1f9a7f64eb4500fbc4dcdb4"
+checksum = "e08e8864a60f06ef0d0ff4ba04124db8b0fb3be5776a5cd47641e942e58c4d43"
 
 [[package]]
 name = "windows_i686_gnu"
-version = "0.42.0"
+version = "0.42.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fbeae19f6716841636c28d695375df17562ca208b2b7d0dc47635a50ae6c5de7"
+checksum = "c61d927d8da41da96a81f029489353e68739737d3beca43145c8afec9a31a84f"
 
 [[package]]
 name = "windows_i686_msvc"
-version = "0.42.0"
+version = "0.42.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "84c12f65daa39dd2babe6e442988fc329d6243fdce47d7d2d155b8d874862246"
+checksum = "44d840b6ec649f480a41c8d80f9c65108b92d89345dd94027bfe06ac444d1060"
 
 [[package]]
 name = "windows_x86_64_gnu"
-version = "0.42.0"
+version = "0.42.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bf7b1b21b5362cbc318f686150e5bcea75ecedc74dd157d874d754a2ca44b0ed"
+checksum = "8de912b8b8feb55c064867cf047dda097f92d51efad5b491dfb98f6bbb70cb36"
 
 [[package]]
 name = "windows_x86_64_gnullvm"
-version = "0.42.0"
+version = "0.42.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "09d525d2ba30eeb3297665bd434a54297e4170c7f1a44cad4ef58095b4cd2028"
+checksum = "26d41b46a36d453748aedef1486d5c7a85db22e56aff34643984ea85514e94a3"
 
 [[package]]
 name = "windows_x86_64_msvc"
-version = "0.42.0"
+version = "0.42.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f40009d85759725a34da6d89a94e63d7bdc50a862acf0dbc7c8e488f1edcb6f5"
+checksum = "9aec5da331524158c6d1a4ac0ab1541149c0b9505fde06423b02f5ef0106b9f0"
 
 [[package]]
 name = "winnow"
diff --git a/tidepool/Cargo.toml b/tidepool/Cargo.toml
index 263230c..37d1d71 100644
--- a/tidepool/Cargo.toml
+++ b/tidepool/Cargo.toml
@@ -20,3 +20,4 @@ toml = { version = "0.7" }
 serde_json = { version = "1.0" }
 clap = { version = "4.0", features = ["derive"] }
 anyhow = { version = "1.0" }
+ctrlc = { version = "3.2" }
diff --git a/tidepool/src/main.rs b/tidepool/src/main.rs
index 10fcf98..a5c35f1 100644
--- a/tidepool/src/main.rs
+++ b/tidepool/src/main.rs
@@ -2,6 +2,8 @@ use anyhow::{Context as _, Result};
 use rand::RngCore as _;
 use std::io::{Read, Write};
 use std::path::Path;
+use std::sync::{atomic, mpsc, Arc};
+use std::time::Duration;
 
 use fish::bot;
 use tidepool::{cli, config, output, sim};
@@ -18,36 +20,81 @@ fn main() -> Result<()> {
     }
 }
 
+#[derive(Debug)]
+enum Msg {
+    Interrupt,
+    Heartbeat(u64),
+    Status(u64, Box<Status>),
+    Done(u64, Box<output::Output>),
+}
+
+#[derive(Debug)]
+struct Status {
+    pieces: usize,
+    lines_left: usize,
+    time: Duration,
+}
+
+fn create_mailbox() -> (mpsc::SyncSender<Msg>, mpsc::Receiver<Msg>) {
+    let (tx, rx) = mpsc::sync_channel(128);
+
+    let tx2 = tx.clone();
+    let on_ctrlc = move || {
+        if tx2.send(Msg::Interrupt).is_err() {
+            tracing::warn!("nobody handled ctrl-c, aborting");
+            std::process::exit(128 + ctrlc::Signal::SIGINT as i32);
+        }
+    };
+    if let Err(err) = ctrlc::set_handler(on_ctrlc) {
+        tracing::warn!("could not set signal handler: {err}");
+    }
+
+    (tx, rx)
+}
+
 fn single(args: cli::SingleRun) -> Result<()> {
     let config = parse_config_file(&args.config_file)?;
 
-    let output = simulation(&args.io, &args.data, args.seed, config);
+    let (tx, rx) = create_mailbox();
+    let exit_early = Arc::new(atomic::AtomicBool::new(false));
 
-    let mut writer: Box<dyn std::io::Write> = match &args.output_file {
-        Some(path) => {
-            if path.is_file() {
-                if prompt_yn(&args.io, "output file already exists, overwrite?") {
-                    tracing::debug!("removing {path:?}");
-                    std::fs::remove_file(path)?;
-                } else {
-                    tracing::warn!("output file already exists, exiting.");
-                    return Ok(());
+    let exit_early2 = exit_early.clone();
+    let config2 = config.clone();
+    std::thread::spawn(move || run_simulation(&args.data, config2, args.seed, 0, tx, exit_early2));
+
+    while let Ok(msg) = rx.recv() {
+        tracing::trace!(msg = debug(&msg));
+
+        match msg {
+            Msg::Interrupt => {
+                eprintln!("\ncaught interrupt.");
+                tracing::debug!("interrupted");
+                exit_early.store(true, atomic::Ordering::Relaxed);
+            }
+            Msg::Heartbeat(_id) => {
+                tracing::debug!("heartbeat");
+            }
+            Msg::Status(_id, status) => {
+                if !args.io.quiet {
+                    let ps = status.pieces;
+                    let ll = status.lines_left;
+                    let pps = ps as f64 / status.time.as_secs_f64();
+                    eprintln!("#{ps}, {ll} lines left, {pps:.2} pps");
                 }
             }
-            Box::new(
-                std::fs::File::create(path)
-                    .with_context(|| format!("error opening output file '{}'", path.display()))?,
-            )
-        }
-        None => Box::new(std::io::stdout()),
-    };
+            Msg::Done(_id, output) => {
+                std::mem::drop(rx);
 
-    let pretty = args.output_file.is_none() && !args.io.quiet;
-    if pretty {
-        serde_json::to_writer_pretty(&mut writer, &output).context("error writing output")?;
-        writeln!(&mut writer).context("error writing output")?;
-    } else {
-        serde_json::to_writer(&mut writer, &output).context("error writing output")?;
+                if output.cleared < config.game.goal {
+                    if !prompt_yn(&args.io, "run did not finish, keep it?") {
+                        break;
+                    }
+                }
+
+                write_output(&args.io, args.output_file.as_deref(), &output)?;
+                break;
+            }
+        }
     }
 
     Ok(())
@@ -67,11 +114,41 @@ fn parse_config_file(path: &Path) -> Result<config::Config> {
     toml::from_str(&contents).context("error parsing config file")
 }
 
-fn prompt_yn(io: &cli::IoArgs, msg: &str) -> bool {
-    if io.noninteractive {
-        return false;
+fn write_output(io_args: &cli::IoArgs, path: Option<&Path>, output: &output::Output) -> Result<()> {
+    let mut writer: Box<dyn std::io::Write> = match &path {
+        Some(path) => {
+            if path.is_file() {
+                if prompt_yn(io_args, "output file already exists, overwrite?") {
+                    tracing::debug!("removing {path:?}");
+                    std::fs::remove_file(path)?;
+                } else {
+                    tracing::warn!("output file already exists, exiting.");
+                    return Ok(());
+                }
+            }
+            Box::new(
+                std::fs::File::create(path)
+                    .with_context(|| format!("error opening output file '{}'", path.display()))?,
+            )
+        }
+        None => Box::new(std::io::stdout()),
+    };
+
+    let pretty = path.is_none() && !io_args.quiet;
+    if pretty {
+        serde_json::to_writer_pretty(&mut writer, &output)
+            .context("error writing output")
+            .and_then(|_| writeln!(&mut writer).context("error writing output"))
+    } else {
+        serde_json::to_writer(&mut writer, &output).context("error writing output")
     }
-    let mut output = std::io::stdout().lock();
+}
+
+fn prompt_yn(io_args: &cli::IoArgs, msg: &str) -> bool {
+    if io_args.noninteractive {
+        return true;
+    }
+    let mut output = std::io::stderr().lock();
     write!(output, "{msg} [y/N] ").unwrap();
     output.flush().unwrap();
     let mut user_input = String::new();
@@ -79,15 +156,15 @@ fn prompt_yn(io: &cli::IoArgs, msg: &str) -> bool {
     user_input.trim().eq_ignore_ascii_case("y")
 }
 
-fn simulation(
-    io: &cli::IoArgs,
-    data: &cli::OutputDataArgs,
-    seed: Option<u64>,
+fn run_simulation(
+    data_args: &cli::OutputDataArgs,
     config: config::Config,
-) -> output::Output {
-    // TODO: status signals
-
-    let mut moves = data.list_moves.then(Vec::new);
+    seed: Option<u64>,
+    id: u64,
+    tx: mpsc::SyncSender<Msg>,
+    exit_early: Arc<atomic::AtomicBool>,
+) {
+    let mut moves = data_args.list_moves.then(Vec::new);
     let seed = seed.unwrap_or_else(|| rand::thread_rng().next_u64());
 
     let sim_opts = sim::Options {
@@ -100,9 +177,8 @@ fn simulation(
     let time_start = std::time::Instant::now();
 
     while sim.lines_left() > 0 {
-        // TODO: progress bar
-        if !io.quiet {
-            eprintln!("#{}, {} left", sim.pieces(), sim.lines_left());
+        if exit_early.load(atomic::Ordering::Relaxed) {
+            break;
         }
 
         let mut bot = bot::Bot::new(
@@ -112,34 +188,53 @@ fn simulation(
 
         for i in 0..config.bot.iters {
             bot.think();
-            if i % 1000 == 999 {
-                tracing::debug!("iteration {i}");
+
+            // periodically check back with the main thread to see if we should exit
+            if i % 4096 == 4095 {
+                if exit_early.load(atomic::Ordering::Relaxed) {
+                    break;
+                }
+                if tx.send(Msg::Heartbeat(id)).is_err() {
+                    break;
+                }
             }
         }
 
-        if let Some(placement) = bot.suggest() {
-            sim.play(placement);
+        let Some(placement) = bot.suggest() else {
+            tracing::warn!("gave up :( pieces={}, id={id}", sim.pieces());
+            break;
+        };
 
-            if let Some(moves) = moves.as_mut() {
-                moves.push(output::Move { placement })
-            }
-        } else {
+        sim.play(placement);
+        if let Some(moves) = moves.as_mut() {
+            moves.push(output::Move { placement })
+        }
+
+        let status = Status {
+            lines_left: sim.lines_left(),
+            pieces: sim.pieces(),
+            time: std::time::Instant::now() - time_start,
+        };
+        if tx.send(Msg::Status(id, status.into())).is_err() {
             break;
         }
     }
 
     let time_end = std::time::Instant::now();
 
-    let profile = data.profile.then(|| output::Profile {
+    let profile = data_args.profile.then(|| output::Profile {
         time: time_end - time_start,
     });
 
-    output::Output {
+    let output = output::Output {
         seed,
         cleared: config.game.goal - sim.lines_left(),
         pieces: sim.pieces(),
         config: config.game,
         moves,
         profile,
+    };
+    if tx.send(Msg::Done(id, output.into())).is_err() {
+        tracing::debug!("nobody received output id={id}");
     }
 }