diff --git a/src/main.rs b/src/main.rs
index 46082ab..1faadd6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,4 @@
-use std::{process::exit, env::Args};
+use std::{process::exit, env::Args, io::{stdin, Read}, sync::mpsc, thread, time::Instant};
 
 static DEFAULT_MAX: usize = 100;
 static DEFAULT_WIDTH: usize = 80;
@@ -9,24 +9,66 @@ fn main() {
         Ok(v ) => v,
         Err(e) => err(&e)
     };
-
-    // [#####....] ---- 50%
     
-    let percent = config.val * 100 / config.max;
+    if let Some(val) = config.val {
+        let bar = generate_bar(val, config.max, config.width, &config.chars, None);
+        println!("{}", bar);
+    } else {
+        let (tx, rx) = mpsc::sync_channel(256);
+        thread::spawn(move || {
+            let mut stdin = stdin();
+            let mut out = [0; 1];
+            loop {
+                if let Ok(count) = stdin.read(&mut out) {
+                    tx.send(count);
+                }
+            }
+        });
+        let mut val = 0;
+        let mut spin = 0;
+        let now = Instant::now();
+        loop {
+            if let Ok(count) = rx.try_recv() {
+                val += count;
+            }
+            let bar = generate_bar_clamp(val, config.max, config.width, &config.chars, Some(spin));
+            print!("\r{}", bar);
+            if val >= config.max {
+                break;
+            }
+            spin = ((now.elapsed().as_millis() / 100) % 6) as usize;
+        }
+    }
+}
+
+fn generate_bar(val: usize, max: usize, width: usize, chars: &Chars, spin: Option<usize>) -> String {
+    let percent = val * 100 / max;
     let percent_str = percent.to_string();
-    let after_bar = format!(" {} {}% ", "-".repeat(6 - percent_str.len()), percent_str);
-    let bar_len = config.width - after_bar.len();
+    let after_bar = if let Some(spin) = spin {
+        format!(" {} {}% {} ", "-".repeat(6 - percent_str.len()), percent_str, if val == max { chars.spin_done() } else { chars.spin(spin) })
+    } else {
+        format!(" {} {}% ", "-".repeat(6 - percent_str.len()), percent_str)
+    };
+    let bar_len = width - after_bar.len();
     let sep = bar_len * percent / 100;
 
     let mut bar = String::new();
 
-    bar.push(if sep > 0 { config.first_char.1 } else { config.first_char.0 });
+    bar.push(chars.first(sep > 0));
     for i in 1..bar_len-1 {
-        bar.push(if sep > i { config.middle_char.1 } else { config.middle_char.0 });
+        bar.push(chars.mid(sep > i));
     }
-    bar.push(if sep > bar_len-1 { config.last_char.1 } else { config.last_char.0 });
+    bar.push(chars.last(sep > bar_len - 1));
 
-    println!("{}{}", bar, after_bar);
+    format!("{}{}", bar, after_bar)
+}
+
+fn generate_bar_clamp(mut val: usize, max: usize, width: usize, chars: &Chars, spin: Option<usize>) -> String {
+    if val > max {
+        val = max;
+    }
+
+    generate_bar(val, max, width, chars, spin)
 }
 
 fn err(msg: &str) -> ! {
@@ -36,16 +78,48 @@ fn err(msg: &str) -> ! {
 }
 
 fn show_help() {
-    eprintln!("Usage: progress <value> [--max <max>] [--width <width>] [--fira]");
+    eprintln!("Usage: progress [<value>] [--max <max>] [--width <width>] [--fira]");
+}
+
+struct Chars {
+    first: (char, char),
+    mid: (char, char),
+    last: (char, char),
+    spin: [char; 6],
+    spin_done: char
+}
+
+impl Chars {
+    fn new(first: (char, char), mid: (char, char), last: (char, char), spin: [char; 6], spin_done: char) -> Self {
+        Self { first, mid, last, spin, spin_done }
+    }
+
+    fn first(&self, filled: bool) -> char {
+        if filled { self.first.1 } else { self.first.0 }
+    }
+
+    fn mid(&self, filled: bool) -> char {
+        if filled { self.mid.1 } else { self.mid.0 }
+    }
+
+    fn last(&self, filled: bool) -> char {
+        if filled { self.last.1 } else { self.last.0 }
+    }
+
+    fn spin(&self, n: usize) -> char {
+        self.spin[n % 6]
+    }
+    
+    fn spin_done(&self) -> char {
+        self.spin_done
+    }
 }
 
 struct Config {
-    val: usize,
+    val: Option<usize>,
     max: usize,
-    first_char: (char, char),
-    middle_char: (char, char),
-    last_char: (char, char),
-    width: usize
+    width: usize,
+    chars: Chars
 }
 
 impl Config {
@@ -53,17 +127,19 @@ impl Config {
         args.next();
         let mut val = None;
         let mut max = None;
-        let mut first_char = ('[', '[');
-        let mut middle_char = ('.', '#');
-        let mut last_char = (']', ']');
         let mut width = None;
+        let mut first_char = ('[', '[');
+        let mut mid_char = ('.', '#');
+        let mut last_char = (']', ']');
+        let mut spin = ['/', '-', '\\', '/', '-', '\\'];
 
         while let Some(next) = args.next() {
             if next.starts_with("--") {
                 if next == "--fira" {
                     first_char = ('\u{ee00}', '\u{ee03}');
-                    middle_char = ('\u{ee01}', '\u{ee04}');
+                    mid_char = ('\u{ee01}', '\u{ee04}');
                     last_char = ('\u{ee02}', '\u{ee05}');
+                    spin = ['\u{ee06}', '\u{ee07}', '\u{ee08}', '\u{ee09}', '\u{ee0a}', '\u{ee0b}'];
                 } else if next == "--max" {
                     if let Some(_) = max { return Err("can only provide 1 max".to_string()) }
                     let next = match args.next() {
@@ -98,18 +174,9 @@ impl Config {
                 }
             }
         }
-
-        let val = match val {
-            Some(v) => v,
-            None => return Err("must provide a value".to_string())
-        };
         
         let max = max.unwrap_or(DEFAULT_MAX);
 
-        if val > max {
-            return Err("value cannot be > max".to_string());
-        }
-
         let width = width.unwrap_or_else(|| termsize::get().map_or(DEFAULT_WIDTH, |v| v.cols.into()));
 
         if width < 11 {
@@ -117,12 +184,8 @@ impl Config {
         }
 
         Ok(Config {
-            val,
-            max,
-            first_char,
-            middle_char,
-            last_char,
-            width
+            val, max, width,
+            chars: Chars::new(first_char, mid_char, last_char, spin, '✓'),
         })
     }
 }
\ No newline at end of file