diff --git a/src/lib/dict.ts b/src/lib/dict.ts
index cb679c9..23215da 100644
--- a/src/lib/dict.ts
+++ b/src/lib/dict.ts
@@ -35,6 +35,11 @@ export class Dict {
 	[Symbol.for("Deno.customInspect")]() {
 		return `Dict { ${this.words.size} words, ${this.letters.size} letters }`;
 	}
+
+	clone() {
+		const words = new Set(this.words.values());
+		return new Dict(words, this.length);
+	}
 }
 
 export function contains_any(text: string, words: string[]) {
diff --git a/src/lib/guesser/reducing.ts b/src/lib/guesser/reducing.ts
new file mode 100644
index 0000000..7c1ab2b
--- /dev/null
+++ b/src/lib/guesser/reducing.ts
@@ -0,0 +1,77 @@
+import { Dict } from "../dict.ts";
+import { GuessResult, Info } from "../game/game.ts";
+import { Value } from "../utils.ts";
+import { Awaitable, enumerate, range, zip } from "../utils.ts";
+import { Guessing } from "./guesser.ts";
+
+export class ReducingGuesser implements Guessing {
+	length;
+	words;
+	possibilities;
+
+	public constructor(words: Dict) {
+		this.words = words;
+		this.length = words.length;
+		this.possibilities = words.clone();
+	}
+
+	public async guess(try_: (guess: string, known: string) => Awaitable<GuessResult>) {
+		const guess = this.make_guess();
+		const result = await try_(guess, "");
+		if (result.kind === "success") return result;
+		this.learn(guess, result.informations);
+		return null;
+	}
+
+	make_guess() {
+		const letters = [...this.words.letters];
+		const letters_ranks = [...range(0, this.length)].map(() => new Map(letters.map((l) => [l, { value: 0 }])));
+		for (const word of this.possibilities.words) {
+			for (const [index, letter] of enumerate(word)) {
+				letters_ranks[index].get(letter)!.value += 1;
+			}
+		}
+		const candidates = [...this.words.words];
+		const scored = candidates.map((word) => [word, score_word_from_ranks(word, letters_ranks)] as const);
+		const [best] = scored.reduce((a, b) => a[1] > b[1] ? a : b);
+		return best;
+	}
+
+	learn(word: string, infos: Info[]) {
+		const to_delete = new Set<string>();
+		const pos = this.possibilities;
+		for (const [index, [letter, info]] of enumerate(zip(word, infos))) {
+			if (info.kind === "there") for (const word of pos.words) if (word[index] !== letter) to_delete.add(word);
+			if (info.kind === "somewhere") for (const word of pos.words) if (word[index] === letter) to_delete.add(word);
+			if (info.kind === "abscent") for (const word of pos.words) if (word.includes(letter)) to_delete.add(word);
+		}
+		for (const d of to_delete) pos.words.delete(d);
+	}
+}
+
+// note : does not take into account knowledge we already have.
+function score_word_from_ranks(word: string, ranks: Map<string, Value<number>>[]) {
+	let result = 0;
+	for (const [index, letter] of enumerate(word)) {
+		// note : bonus for ANY letter.
+		for (const index_ranks of ranks) {
+			const letter_rank = index_ranks.get(letter)!.value;
+			result += letter_rank;
+		}
+		// note : bonus for THIS letter.
+		const index_ranks = ranks[index];
+		const letter_rank = index_ranks.get(letter)!.value;
+		result += letter_rank;
+	}
+	return result;
+}
+
+/*
+note : The algorithm must proceed as follow :
+
+1. establish a list of possible words
+2. loop :
+	2.1 for each word, for each letter, estimate by how much this letter cuts possibilities for all three possible outcomes.
+	(2.1-bis weigts those scores by the frequency of the word ?)
+	2.2 play the word which individual letters cuts most of the possible space.
+ */
diff --git a/src/lib/utils.ts b/src/lib/utils.ts
index be4f837..f1a64c5 100644
--- a/src/lib/utils.ts
+++ b/src/lib/utils.ts
@@ -30,3 +30,5 @@ export function last<T>(iterable: Iterable<T>) {
 	for (const item of iterable) last = item;
 	return last;
 }
+
+export type Value<T> = { value: T };