diff --git a/Cargo.toml b/Cargo.toml
index 671297c..71fdfb9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -28,6 +28,7 @@ clap = { version = "4.5.3", features = ["derive"], optional = true }
 colored = { version = "2.1.0", optional = false }
 libpt = "0.4.2"
 rand = "0.8.5"
+regex = "1.10.3"
 serde = { version = "1.0.197", optional = true, features = ["serde_derive"] }
 serde_json = { version = "1.0.114", optional = true }
 thiserror = "1.0.58"
diff --git a/src/bin/game/cli.rs b/src/bin/game/cli.rs
index 9072152..a2c179f 100644
--- a/src/bin/game/cli.rs
+++ b/src/bin/game/cli.rs
@@ -54,8 +54,8 @@ fn main() -> anyhow::Result<()> {
         response = match game.guess(guess) {
             Ok(r) => r,
             Err(err) => match err {
-                GameError::GuessHasWrongLength => {
-                    println!("word length: must be {} long", game.length());
+                GameError::GuessHasWrongLength(len) => {
+                    println!("word length: must be {} long but is {}", game.length(), len);
                     continue;
                 }
                 _ => {
diff --git a/src/error.rs b/src/error.rs
index ab98955..4a287d5 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -1,5 +1,7 @@
 use thiserror::Error;
 
+use crate::wlist::word::Word;
+
 pub type WResult<T> = std::result::Result<T, Error>;
 pub type GameResult<T> = std::result::Result<T, GameError>;
 
@@ -18,12 +20,19 @@ pub enum Error {
     // for `FromStr` of `BuiltinSolver`
     #[error("Unknown builtin solver")]
     UnknownBuiltinSolver,
+    #[error("pattern matching error")]
+    Regex{
+        #[from]
+        source: regex::Error
+    }
 }
 
 #[derive(Debug, Clone, Error)]
 pub enum GameError {
-    #[error("The guess has the wrong length")]
-    GuessHasWrongLength,
+    #[error("The guess has the wrong length ({0})")]
+    GuessHasWrongLength(usize),
     #[error("The game is finished but a guess is being made")]
     TryingToPlayAFinishedGame,
+    #[error("Tried to guess a word that is not in the wordlist ({0})")]
+    WordNotInWordlist(Word),
 }
diff --git a/src/game/mod.rs b/src/game/mod.rs
index f40107c..f8ebcaa 100644
--- a/src/game/mod.rs
+++ b/src/game/mod.rs
@@ -78,11 +78,14 @@ impl<'wl, WL: WordList> Game<'wl, WL> {
     /// if the game is finished.
     pub fn guess(&mut self, guess: Word) -> GameResult<GuessResponse> {
         if guess.len() != self.length {
-            return Err(GameError::GuessHasWrongLength);
+            return Err(GameError::GuessHasWrongLength(guess.len()));
         }
         if self.finished || self.step > self.max_steps {
             return Err(GameError::TryingToPlayAFinishedGame);
         }
+        if self.wordlist.get_word(&guess).is_none() {
+            return Err(GameError::WordNotInWordlist(guess));
+        }
         self.step += 1;
 
         let mut compare_solution = self.solution.0.clone();
@@ -101,7 +104,8 @@ impl<'wl, WL: WordList> Game<'wl, WL> {
             evaluation.push((c, status));
         }
 
-        let mut response = GuessResponse::new(guess, evaluation, &self);
+        let response = GuessResponse::new(guess, evaluation, self);
+        self.responses.push(response.clone());
         self.finished = response.finished();
         Ok(response)
     }
@@ -128,6 +132,13 @@ impl<'wl, WL: WordList> Game<'wl, WL> {
     pub fn responses(&self) -> &Vec<GuessResponse> {
         &self.responses
     }
+    pub fn last_response(&self) -> Option<&GuessResponse> {
+        self.responses().last()
+    }
+
+    pub fn wordlist(&self) -> &WL {
+        self.wordlist
+    }
 }
 
 /// Build and Configure a [`Game`]
diff --git a/src/game/response.rs b/src/game/response.rs
index d14f02c..6966b87 100644
--- a/src/game/response.rs
+++ b/src/game/response.rs
@@ -62,6 +62,14 @@ impl GuessResponse {
             None
         }
     }
+
+    pub fn evaluation(&self) -> &[(char, Status)] {
+        &self.evaluation
+    }
+
+    pub fn guess(&self) -> &str {
+        &self.guess
+    }
 }
 
 impl Display for GuessResponse {
diff --git a/src/solve/naive/mod.rs b/src/solve/naive/mod.rs
index a8c98de..bc2f9e3 100644
--- a/src/solve/naive/mod.rs
+++ b/src/solve/naive/mod.rs
@@ -3,7 +3,7 @@ use libpt::log::info;
 use crate::wlist::word::Word;
 use crate::wlist::WordList;
 
-use super::{AnyBuiltinSolver, Solver};
+use super::{AnyBuiltinSolver, Solver, Status};
 
 #[derive(Debug, Clone)]
 pub struct NaiveSolver<'wl, WL> {
@@ -16,7 +16,21 @@ impl<'wl, WL: WordList> Solver<'wl, WL> for NaiveSolver<'wl, WL> {
         Ok(Self { wl: wordlist })
     }
     fn guess_for(&self, game: &crate::game::Game<WL>) -> Word {
-        self.wl.rand_word().0
+        // HACK: hardcoded length
+        let mut buf: Word = Word::from(".....");
+        let response = game.last_response();
+        if response.is_some() {
+            for (idx, p) in response.unwrap().evaluation().iter().enumerate() {
+                if p.1 == Status::Matched {
+                    buf.replace_range(idx..idx + 1, &p.0.to_string());
+                }
+            }
+        }
+        game.wordlist()
+            .get_words_matching(buf)
+            .expect("the solution does not exist in the wordlist")[0]
+            .0
+            .clone()
     }
 }
 
diff --git a/src/wlist/builtin.rs b/src/wlist/builtin.rs
index 2e5e855..3204376 100644
--- a/src/wlist/builtin.rs
+++ b/src/wlist/builtin.rs
@@ -19,7 +19,7 @@ impl super::WordList for BuiltinWList {
         &self.words
     }
     fn get_word(&self, word: &Word) -> Option<super::WordData> {
-        self.words.get(&word)
+        self.words.get(word)
     }
 }
 
diff --git a/src/wlist/mod.rs b/src/wlist/mod.rs
index 2cd029c..ab795b2 100644
--- a/src/wlist/mod.rs
+++ b/src/wlist/mod.rs
@@ -1,5 +1,8 @@
+use libpt::log::debug;
 use rand::seq::IteratorRandom;
 
+use regex::Regex;
+
 use std::collections::HashMap;
 use std::ops::RangeBounds;
 
@@ -14,13 +17,16 @@ pub type AnyWordlist = Box<dyn WordList>;
 
 pub trait WordList: Clone + std::fmt::Debug + Default {
     fn solutions(&self) -> ManyWordDatas {
-        let wmap = self.wordmap();
+        let wmap = self.wordmap().clone();
         let threshold = wmap.threshold();
-        wmap.iter().filter(|i| *i.1 > threshold).collect()
+        wmap.iter()
+            .filter(|i| *i.1 > threshold)
+            .map(|p| (p.0.clone(), *p.1))
+            .collect()
     }
     fn rand_solution(&self) -> WordData {
         let mut rng = rand::thread_rng();
-        let sol = *self.solutions().iter().choose(&mut rng).unwrap();
+        let sol = self.solutions().iter().choose(&mut rng).unwrap().clone();
         (sol.0.to_owned(), sol.1.to_owned())
     }
     fn rand_word(&self) -> WordData {
@@ -62,4 +68,28 @@ pub trait WordList: Clone + std::fmt::Debug + Default {
         let n: f64 = cmap.keys().len() as f64;
         cmap.into_iter().map(|p| (p.0, p.1 as f64 / n)).collect()
     }
+    fn raw_wordlist(&self) -> String {
+        let mut buf = String::new();
+        for w in self.wordmap().keys() {
+            buf += &w;
+            buf += "\n";
+        }
+        buf
+    }
+    fn get_words_matching(&self, pattern: String) -> WResult<ManyWordDatas> {
+        let pattern = Regex::new(&pattern)?;
+        let hay = self.raw_wordlist();
+        let keys = pattern.captures_iter(&hay);
+        let mut buf = ManyWordDatas::new();
+        for k in keys {
+            debug!("match: {k:?}");
+            let w: WordData = self.wordmap().get(&k[0]).unwrap();
+            buf.push(w)
+        }
+        // sort by frequency
+        buf.sort_by(|a, b| {
+            a.1.partial_cmp(&b.1).unwrap()
+        });
+        Ok(buf)
+    }
 }
diff --git a/src/wlist/word.rs b/src/wlist/word.rs
index 2385a2e..91128d4 100644
--- a/src/wlist/word.rs
+++ b/src/wlist/word.rs
@@ -1,5 +1,6 @@
 use std::collections::HashMap;
 use std::fmt::write;
+use std::hash::Hash;
 
 use libpt::log::debug;
 #[cfg(feature = "serde")]
@@ -11,7 +12,7 @@ pub type Frequency = f64;
 pub type Word = String;
 pub type WordData = (Word, Frequency);
 pub type ManyWords<'a> = Vec<&'a Word>;
-pub type ManyWordDatas<'a> = Vec<(&'a Word, &'a Frequency)>;
+pub type ManyWordDatas = Vec<(Word, Frequency)>;
 
 #[derive(Clone)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
@@ -66,9 +67,9 @@ impl WordMap {
     pub fn inner(&self) -> &HashMap<Word, Frequency> {
         &self.inner
     }
-    pub fn get(&self, word: &Word) -> Option<WordData> {
-        match self.inner.get(word) {
-            Some(f) => Some((word.clone(), *f)),
+    pub fn get<I: std::fmt::Display>(&self, word: I) -> Option<WordData> {
+        match self.inner.get(&word.to_string()) {
+            Some(f) => Some((word.to_string(), *f)),
             None => None,
         }
     }
@@ -104,7 +105,7 @@ impl From<HashMap<Word, Frequency>> for WordMap {
     }
 }
 
-impl From<WordMap > for HashMap<Word, Frequency>{
+impl From<WordMap> for HashMap<Word, Frequency> {
     fn from(value: WordMap) -> Self {
         value.inner
     }