diff --git a/.prettierignore b/.prettierignore
new file mode 100644
index 0000000..0a353ed
--- /dev/null
+++ b/.prettierignore
@@ -0,0 +1 @@
+**/*.md
\ No newline at end of file
diff --git a/package.json b/package.json
index 58b5f52..030700c 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "postcss-contains",
-  "version": "0.0.1",
+  "version": "0.1.0",
   "description": "A PostCSS plugin to styles selectors based on specific declaration or property.",
   "keywords": [
     "postcss",
@@ -27,7 +27,7 @@
     "test": "vitest run",
     "ci": "npm run build && npm run check-format && npm run test"
   },
-  "dependencies": {
+  "peerDependencies": {
     "postcss": "^8.4.47"
   },
   "devDependencies": {
diff --git a/readme.md b/readme.md
index ef0b500..ba5cf08 100644
--- a/readme.md
+++ b/readme.md
@@ -7,21 +7,23 @@ The `@contains` at-rule targets elements and selectors when they _contain_:
 - A specific property (e.g. `position` or `margin`)
 - A specific declaration (property-value pair, e.g. `display: grid`)
 
+
 ## Installation
 
 ```sh
 npm install postcss-contains --save-dev
 ```
 
+
 ## Usage
 
 ```js
 // postcss.config.js
-import postcssContains from "postcss-contains";
+import postcssContains from "postcss-contains"
 
 export default {
   plugins: [postcssContains],
-};
+}
 ```
 
 ```css
@@ -86,6 +88,7 @@ div {
 }
 ```
 
+
 ### Duplications
 
 When two `@contains` rules target the same property or declaration, their styles will merge by default.
@@ -134,6 +137,7 @@ div {
 
 See [options](#options) for more.
 
+
 ### Specificity
 
 "Property-value" matches considered with a specificity so they take precedence over "property-only" matches.
@@ -169,6 +173,7 @@ span {
 }
 ```
 
+
 ## Options
 
 #### `duplication`
@@ -236,16 +241,13 @@ div {
 
 ```css
 /* a */
-@contains (color) {
-}
+@contains (color) {}
 
 /* b */
-@contains (color: red) {
-}
+@contains (color: red) {}
 
 /* c */
-@contains (color: red) {
-}
+@contains (color: red) {}
 ```
 
 More examples are provided [here](./test/exmaples.md).
diff --git a/src/contains.ts b/src/contains.ts
index 12fec7a..bdbc79c 100644
--- a/src/contains.ts
+++ b/src/contains.ts
@@ -179,87 +179,85 @@ export default class Contains {
   }
 
   // 1) collecting all @contains: conditions and their declarations
-  collect(root: Root, result: Result) {
-    root.walkAtRules("contains", (atRule: AtRule) => {
-      const params = getParams(atRule.params);
-      const overrides = atRule.params.startsWith("overrides");
-
-      if (/\n/.test(atRule.params)) {
-        atRule.warn(
-          result,
-          "It's better to not use new lines inside @contains params.",
-        );
-      }
+  collect(atRule: AtRule, result: Result) {
+    const params = getParams(atRule.params);
+    const overrides = atRule.params.startsWith("overrides");
+
+    if (/\n/.test(atRule.params)) {
+      atRule.warn(
+        result,
+        "It's better to not use new lines inside @contains params.",
+      );
+    }
 
-      if (!atRule.nodes) {
-        throw new Error(
-          `@contains has no styles (provided no curly brackets).\n   ${atRule.toString()}`,
-        );
-      }
+    if (!atRule.nodes) {
+      throw atRule.error(
+        `@contains has no styles (provided no curly brackets).\n   ${atRule.toString()}`,
+      );
+    }
 
-      if (atRule.nodes.length === 0) {
-        atRule.warn(result, `The @contains was empty; it provides no styles.`);
-      }
+    if (atRule.nodes.length === 0) {
+      atRule.warn(result, `The @contains was empty; it provides no styles.`);
+    }
 
-      const isInvalidType = atRule.nodes.some(
-        (child) => child.type === "rule" || child.type === "atrule",
+    const isInvalidType = atRule.nodes.some(
+      (child) => child.type === "rule" || child.type === "atrule",
+    );
+
+    if (isInvalidType) {
+      throw atRule.error(
+        `rules and at-rules can not be nested inside @contains.\n   ${atRule.toString()}`,
       );
+    }
 
-      if (isInvalidType) {
-        throw new Error(
-          `rules and at-rules can not be nested inside @contains.\n   ${atRule.toString()}`,
+    if (params.includes(":")) {
+      const { property, value } = extract(params, "pair");
+
+      if (!property || !value) {
+        throw atRule.error(
+          `Something went wrong on \t ${atRule.toString()} \n\t >>> property: ${property} - value: ${value}`,
         );
       }
 
-      if (params.includes(":")) {
-        const { property, value } = extract(params, "pair");
-
-        if (!property || !value) {
-          throw new Error(
-            `Something went wrong on \t ${atRule.toString()} \n\t >>> property: ${property} - value: ${value}`,
-          );
-        }
-
-        const variant: "pair" | "single" = "pair";
-        const declarations = new Map<string, string>();
+      const variant: "pair" | "single" = "pair";
+      const declarations = new Map<string, string>();
 
-        for (const node of atRule.nodes) {
-          if (node.type === "decl") {
-            const { prop, value, important } = node;
-            // const declaration = new Declaration({ prop, value, important });
-            declarations.set(prop, value);
-          }
+      for (const node of atRule.nodes) {
+        if (node.type === "decl") {
+          const { prop, value, important } = node;
+          // const declaration = new Declaration({ prop, value, important });
+          declarations.set(prop, value);
         }
+      }
 
-        const bucket = { value, variant, overrides, declarations };
-        this.add(property, bucket);
-        atRule.remove();
-        return;
-      } else {
-        const { property } = extract(params, "single");
+      const bucket = { value, variant, overrides, declarations };
+      this.add(property, bucket);
+      atRule.remove();
+      return;
+    } else {
+      const { property } = extract(params, "single");
 
-        if (!property) {
-          throw new Error(
-            `Something went wrong on \t ${atRule.toString()} \n\t >>> property: ${property}`,
-          );
-        }
+      if (!property) {
+        throw atRule.error(
+          `Something went wrong on \t ${atRule.toString()} \n\t >>> property: ${property}`,
+        );
+      }
 
-        const variant: "pair" | "single" = "single";
-        const declarations = new Map<string, string>();
+      const variant: "pair" | "single" = "single";
+      const declarations = new Map<string, string>();
 
-        for (const node of atRule.nodes) {
-          if (node.type === "decl") {
-            const { prop, value, important } = node;
-            declarations.set(prop, value);
-          }
+      for (const node of atRule.nodes) {
+        if (node.type === "decl") {
+          const { prop, value, important } = node;
+          declarations.set(prop, value);
         }
-
-        const bucket = { value: null, variant, overrides, declarations };
-        this.add(property, bucket);
-        atRule.remove();
-        return;
       }
-    });
+
+      const bucket = { value: null, variant, overrides, declarations };
+      this.add(property, bucket);
+      atRule.remove();
+      return;
+    }
   }
 
   add(property: string, bucket: Bucket) {
diff --git a/src/index.ts b/src/index.ts
index e2263d6..1d25fea 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -14,8 +14,10 @@ const plugin: PluginCreator<PluginOptions> = (opts?: PluginOptions) => {
   return {
     postcssPlugin: "postcss-contains",
 
-    Once(root, { result }) {
-      contains.collect(root, result);
+    AtRule: {
+      contains(atRule, { result }) {
+        contains.collect(atRule, result);
+      },
     },
 
     Rule(rule) {
diff --git a/test/exmaples.md b/test/exmaples.md
index 1d136e2..3893f8f 100644
--- a/test/exmaples.md
+++ b/test/exmaples.md
@@ -42,7 +42,7 @@
 - No property or declaration passed to @contains
 
 ```css
-@Contains() {
+@Contains () {
   /* styles */
 }
 ```
diff --git a/tsconfig.json b/tsconfig.json
index aa2e23e..e96d34f 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -19,5 +19,5 @@
     "outDir": "dist",
     "sourceMap": true
   },
-  "exclude": ["dist", "test"]
+  "include": ["src"]
 }