diff --git a/package.json b/package.json
index f5456e5..acfabd9 100644
--- a/package.json
+++ b/package.json
@@ -62,7 +62,7 @@
     "husky": "^7.0.1",
     "size-limit": "^5.0.1",
     "tsdx": "^0.14.1",
-    "tslib": "^2.3.0",
-    "typescript": "^4.3.5"
+    "tslib": "^2.3.1",
+    "typescript": "^4.6.3"
   }
 }
diff --git a/src/grid.ts b/src/grid.ts
index 04f33ef..5415154 100644
--- a/src/grid.ts
+++ b/src/grid.ts
@@ -25,7 +25,7 @@ export function grid_traverse_initStep(
   t1: number,
   t2: number
 ): [number, number, number] {
-  let v: number = t2 - t1;
+  const v: number = t2 - t1;
 
   if (v > 0) return [1, cellSize / v, ((ct + v) * cellSize - t1) / v];
   else if (v < 0)
@@ -39,37 +39,37 @@ export function grid_traverse(
   y1: number,
   x2: number,
   y2: number,
-  f: any
+  traverseFunction: (cx: number, cy: number) => void
 ): void {
-  let [cx1, cy1] = grid_toCell(cellSize, x1, y1);
-  let [cx2, cy2] = grid_toCell(cellSize, x2, y2);
+  const [cx1, cy1] = grid_toCell(cellSize, x1, y1);
+  const [cx2, cy2] = grid_toCell(cellSize, x2, y2);
   let [stepX, dx, tx] = grid_traverse_initStep(cellSize, cx1, x1, x2);
   let [stepY, dy, ty] = grid_traverse_initStep(cellSize, cy1, y1, y2);
   let [cx, cy] = [cx1, cy1];
 
-  f(cx, cy);
+  traverseFunction(cx, cy);
 
-  //The default implementation had an infinite loop problem when
-  //approaching the last cell in some occassions.We finish iterating
-  //when we are * next * to the last cell
+  // The default implementation had an infinite loop problem when
+  // approaching the last cell in some occassions. We finish iterating
+  // when we are *next* to the last cell.
   do {
     if (tx < ty) {
       [tx, cx] = [tx + dx, cx + stepX];
 
-      f(cx, cy);
+      traverseFunction(cx, cy);
     } else {
       // Addition: include both cells when going through corners
-      if (tx == ty) f(cx + stepX, cy);
+      if (tx == ty) traverseFunction(cx + stepX, cy);
 
       ty = ty + dy;
       cy = cy + stepY;
 
-      f(cx, cy);
+      traverseFunction(cx, cy);
     }
   } while (Math.abs(cx - cx2) + Math.abs(cy - cy2) > 1);
 
   //If we have not arrived to the last cell, use it
-  if (cx != cx2 || cy != cy2) f(cx2, cy2);
+  if (cx != cx2 || cy != cy2) traverseFunction(cx2, cy2);
 }
 
 export function grid_toCellRect(
@@ -81,8 +81,8 @@ export function grid_toCellRect(
 ): [number, number, number, number] {
   let [cx, cy] = grid_toCell(cellSize, x, y);
 
-  const cr = Math.ceil((x + w) / cellSize);
-  const cb = Math.ceil((y + h) / cellSize);
+  const cr: number = Math.ceil((x + w) / cellSize);
+  const cb: number = Math.ceil((y + h) / cellSize);
 
   return [cx, cy, cr - cx + 1, cb - cy + 1];
 }
diff --git a/src/helpers/generic/assertIsPositiveNumber.ts b/src/helpers/generic/assertIsPositiveNumber.ts
index b0dcd1f..f15809d 100644
--- a/src/helpers/generic/assertIsPositiveNumber.ts
+++ b/src/helpers/generic/assertIsPositiveNumber.ts
@@ -1,11 +1,9 @@
-export default function assertIsPositiveNumber(value: any, name: string): void {
+export default function assertIsPositiveNumber(
+  value: number,
+  name: string
+): void {
   if (isNaN(value) || value <= 0)
     throw new Error(
-      name +
-        ' must be a positive integer, but was ' +
-        value +
-        ' (' +
-        typeof value +
-        ')'
+      `"${name}" must be a positive integer, but was ${value} (${typeof value})`
     );
 }
diff --git a/src/helpers/generic/assertType.ts b/src/helpers/generic/assertType.ts
index 9624862..99865b7 100644
--- a/src/helpers/generic/assertType.ts
+++ b/src/helpers/generic/assertType.ts
@@ -1,6 +1,6 @@
 export default function assertType(desiredType: string, value: any, name: string): void {
   if (typeof value !== desiredType)
     throw new Error(
-      `${name} must be a ${desiredType}, but was a ${value} (${typeof value})`
+      `"${name}" must be a ${desiredType}, but was a ${value} (${typeof value})`
     );
 }
diff --git a/src/helpers/world/responses.ts b/src/helpers/world/responses.ts
index b2d0aae..4db4e2a 100644
--- a/src/helpers/world/responses.ts
+++ b/src/helpers/world/responses.ts
@@ -1,6 +1,6 @@
-import { Coords, World } from '../../index';
+import { Collision, ICoords, World } from '../../index';
 
-type ResponseType = (
+export type Response = (
   world: World,
   col: any,
   x: number,
@@ -10,11 +10,17 @@ type ResponseType = (
   goalX: number,
   goalY: number,
   filter: any
-) => [number, number, any, number];
+) => { x: number; y: number; collisions: Collision[] };
 
 export function touch(
   _world: World,
-  col: any,
+  column: {
+    touch: ICoords;
+    move: ICoords;
+    normal: ICoords;
+    slide: ICoords;
+    item: any;
+  },
   _x: number,
   _y: number,
   _w: number,
@@ -22,13 +28,19 @@ export function touch(
   _goalX: number,
   _goalY: number,
   _filter: any
-): { x: number; y: number; collisions: any[] } {
-  return { x: col.touch.x, y: col.touch.y, collisions: [] };
+): { x: number; y: number; collisions: Collision[] } {
+  return { x: column.touch.x, y: column.touch.y, collisions: [] };
 }
 
 export function cross(
   world: any,
-  col: any,
+  column: {
+    touch: ICoords;
+    move: ICoords;
+    normal: ICoords;
+    slide: ICoords;
+    item: any;
+  },
   x: number,
   y: number,
   w: number,
@@ -36,15 +48,30 @@ export function cross(
   goalX: number,
   goalY: number,
   filter: any
-): { x: number; y: number; collisions: any[] } {
-  const collisions = world.project(col.item, x, y, w, h, goalX, goalY, filter);
+): { x: number; y: number; collisions: Collision[] } {
+  const collisions = world.project(
+    column.item,
+    x,
+    y,
+    w,
+    h,
+    goalX,
+    goalY,
+    filter
+  );
 
   return { x: goalX, y: goalY, collisions };
 }
 
 export function slide(
   world: World,
-  col: any,
+  column: {
+    touch: ICoords;
+    move: ICoords;
+    normal: ICoords;
+    slide: ICoords;
+    item: any;
+  },
   x: number,
   y: number,
   w: number,
@@ -52,24 +79,24 @@ export function slide(
   goalX: number,
   goalY: number,
   filter?: any
-): { x: number; y: number; collisions: any[] } {
+): { x: number; y: number; collisions: Collision[] } {
   let _goalX: number = isNaN(goalX) ? x : goalX;
   let _goalY: number = isNaN(goalY) ? y : goalY;
 
-  const tch: Coords = col.touch;
-  const move: Coords = col.move;
+  const tch: ICoords = column.touch;
+  const move: ICoords = column.move;
 
   if (move.x !== 0 || move.y !== 0)
-    if (col.normal.x !== 0) _goalX = tch.x;
+    if (column.normal.x !== 0) _goalX = tch.x;
     else _goalY = tch.y;
 
-  col.slide = { x: _goalX, y: _goalY };
+  column.slide = { x: _goalX, y: _goalY };
 
   const _x: number = tch.x;
   const _y: number = tch.y;
 
   const collisions = world.project(
-    col.item,
+    column.item,
     _x,
     _y,
     w,
@@ -92,7 +119,7 @@ export function bounce(
   goalX?: number,
   goalY?: number,
   filter?: any
-): { x: number; y: number; collisions: any[] } {
+): { x: number; y: number; collisions: Collision[] } {
   const _goalX: number = isNaN(goalX as number) ? x : goalX!;
   const _goalY: number = isNaN(goalY as number) ? y : goalY!;
 
diff --git a/src/helpers/world/sortByTiAndDistance.ts b/src/helpers/world/sortByTiAndDistance.ts
index 000592d..77cd9e5 100644
--- a/src/helpers/world/sortByTiAndDistance.ts
+++ b/src/helpers/world/sortByTiAndDistance.ts
@@ -1,4 +1,4 @@
-import { Rect } from '../..';
+import { IRect } from '../..';
 import { rect_getSquareDistance } from '../../rect';
 
 interface Item {
@@ -7,15 +7,15 @@ interface Item {
   // w: number;
   // h: number;
   ti: number;
-  itemRect: Rect;
-  otherRect: Rect;
+  itemRect: IRect;
+  otherRect: IRect;
 }
 
 export default function sortByTiAndDistance(a: Item, b: Item): number {
   if (a.ti === b.ti) {
-    const ir: Rect = a.itemRect;
-    const ar: Rect = a.otherRect;
-    const br: Rect = b.otherRect;
+    const ir: IRect = a.itemRect;
+    const ar: IRect = a.otherRect;
+    const br: IRect = b.otherRect;
 
     const ad = rect_getSquareDistance(
       ir.x,
diff --git a/src/index.ts b/src/index.ts
index 4b1a79d..57c2ccc 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -15,21 +15,34 @@ import {
   grid_traverse,
 } from './grid';
 import assertIsRect from './helpers/generic/assertIsRect';
-import { bounce, cross, slide, touch } from './helpers/world/responses';
+import {
+  bounce,
+  cross,
+  Response,
+  slide,
+  touch,
+} from './helpers/world/responses';
 import sortByTiAndDistance from './helpers/world/sortByTiAndDistance';
 
 function defaultFilter(): string {
   return 'slide';
 }
 
-export interface Rect {
+interface IItemInfo {
+  item: string;
+  ti1: number;
+  ti2: number;
+  weight: number;
+}
+
+export interface IRect {
   x: number;
   y: number;
   w: number;
   h: number;
 }
 
-export interface Coords {
+export interface ICoords {
   x: number;
   y: number;
 }
@@ -40,18 +53,23 @@ export interface Collision {
   type?: 'touch' | 'cross' | 'slide' | 'bounce' | string;
   overlaps: boolean;
   ti: number;
-  move: Coords;
-  normal: Coords;
-  touch: Coords;
-  itemRect: Rect;
-  otherRect: Rect;
-  slide?: Coords;
-  bounce?: Coords;
+  move: ICoords;
+  normal: ICoords;
+  touch: ICoords;
+  itemRect: IRect;
+  otherRect: IRect;
+  slide?: ICoords;
+  bounce?: ICoords;
 }
 
-export type Cell = { ID: string; x: number; y: number; items: any[] };
+export type Cell = {
+  ID: string;
+  x: number;
+  y: number;
+  items: { [itemID: string]: boolean };
+};
 
-function sortByWeight(a: any, b: any): number {
+function sortByWeight(a: IItemInfo, b: IItemInfo): number {
   return a.weight - b.weight;
 }
 
@@ -62,14 +80,14 @@ function getCellsTouchedBySegment(
   x2: number,
   y2: number
 ): Cell[] {
-  let cells: Cell[] = [];
-  let visited: { [itemID: string]: boolean } = {};
+  const cells: Cell[] = [];
+  const visited: { [itemID: string]: boolean } = {};
 
   grid_traverse(self.cellSize, x1, y1, x2, y2, function(
     cx: number,
     cy: number
   ) {
-    let row: any[] = self.rows[cy];
+    let row: Cell[] = self.rows[cy];
 
     if (!row) return;
 
@@ -97,7 +115,7 @@ function getInfoAboutItemsTouchedBySegment(
   let rect, l, t, w, h, ti1, ti2;
 
   let visited: { [itemID: string]: boolean } = {};
-  let itemInfo: any[] = [];
+  let itemInfo: IItemInfo[] = [];
 
   for (const cell of cells) {
     if (cell?.items)
@@ -148,8 +166,8 @@ function getInfoAboutItemsTouchedBySegment(
 
               itemInfo.push({
                 item: itemID,
-                ti1: ti1,
-                ti2: ti2,
+                ti1: ti1!,
+                ti2: ti2!,
                 weight: Math.min(tii0 || 0, tii1 || 0),
               });
             }
@@ -162,10 +180,10 @@ function getInfoAboutItemsTouchedBySegment(
 }
 
 export class World {
-  responses: { [responseID: string]: any } = {};
+  responses: { [responseID: string]: Response } = {};
   cellSize: number = 0;
-  rows: any[][];
-  rects: { [itemID: string]: Rect };
+  rows: Cell[][];
+  rects: { [itemID: string]: IRect };
   nonEmptyCells: { [cellID: string]: boolean };
 
   constructor(input: {
@@ -182,7 +200,10 @@ export class World {
     this.responses = input.responses;
   }
 
-  addResponse(name: string, response: any): void {
+  addResponse(
+    name: 'bounce' | 'slide' | 'cross' | 'touch',
+    response: Response
+  ): void {
     this.responses[name] = response;
   }
 
@@ -203,7 +224,7 @@ export class World {
     h: number,
     goalX?: number,
     goalY?: number,
-    filter?: (...args: any[]) => any
+    filter?: (...args: any[]) => string
   ): Collision[] {
     assertIsRect(x, y, w, h);
 
@@ -277,7 +298,7 @@ export class World {
   countCells(): number {
     let count = 0;
 
-    for (const row of this.rows.filter((row) => !!row))
+    for (const row of this.rows.filter(row => !!row))
       for (const _col of row) if (!!_col) count++;
 
     return count;
@@ -287,8 +308,8 @@ export class World {
     return !!this.rects[item];
   }
 
-  getItems(): Rect[] {
-    return Object.keys(this.rects).map((rectID) => this.rects[rectID]);
+  getItems(): IRect[] {
+    return Object.keys(this.rects).map(rectID => this.rects[rectID]);
   }
 
   countItems(): number {
@@ -316,7 +337,7 @@ export class World {
     if (!cell.items[itemID]) cell.items[itemID] = true;
   }
 
-  getRect(itemID: string): Rect {
+  getRect(itemID: string): IRect {
     let rect = this.rects[itemID];
 
     if (!rect)
@@ -513,7 +534,7 @@ export class World {
   }
 
   add(itemID: string, x: number, y: number, w: number, h: number): string {
-    let rect: Rect = this.rects[itemID];
+    const rect: IRect = this.rects[itemID];
 
     if (rect) throw new Error(`Item "${itemID}" added to the world twice.`);
 
@@ -521,7 +542,7 @@ export class World {
 
     this.rects[itemID] = { x, y, w, h };
 
-    let [cl, ct, cw, ch] = grid_toCellRect(this.cellSize, x, y, w, h);
+    const [cl, ct, cw, ch] = grid_toCellRect(this.cellSize, x, y, w, h);
 
     for (let cy = ct; cy < ct + ch; cy++)
       for (let cx = cl; cx < cl + cw; cx++) this.addItemToCell(itemID, cx, cy);
@@ -530,7 +551,7 @@ export class World {
   }
 
   remove(itemID: string): void {
-    const itemRect: Rect = JSON.parse(JSON.stringify(this.getRect(itemID)));
+    const itemRect: IRect = JSON.parse(JSON.stringify(this.getRect(itemID)));
 
     delete this.rects[itemID];
 
@@ -547,13 +568,19 @@ export class World {
         this.removeItemFromCell(itemID, cx, cy);
   }
 
-  update(itemID: string, x2: number, y2: number, w2?: any, h2?: number): void {
+  update(
+    itemID: string,
+    x2: number,
+    y2: number,
+    w2?: number,
+    h2?: number
+  ): void {
     let itemRect = this.getRect(itemID);
 
     w2 = isNaN(w2 as number) ? itemRect.w : w2;
     h2 = isNaN(h2 as number) ? itemRect.h : h2;
 
-    assertIsRect(x2, y2, w2, h2!);
+    assertIsRect(x2, y2, w2!, h2!);
 
     if (
       itemRect.x != x2 ||
@@ -561,7 +588,7 @@ export class World {
       itemRect.w != w2 ||
       itemRect.h != h2
     ) {
-      let [cl1, ct1, cw1, ch1] = grid_toCellRect(
+      const [cl1, ct1, cw1, ch1] = grid_toCellRect(
         this.cellSize,
         itemRect.x,
         itemRect.y,
@@ -569,20 +596,20 @@ export class World {
         itemRect.h
       );
 
-      let [cl2, ct2, cw2, ch2] = grid_toCellRect(
+      const [cl2, ct2, cw2, ch2] = grid_toCellRect(
         this.cellSize,
         x2,
         y2,
-        w2,
+        w2!,
         h2!
       );
 
       if (cl1 != cl2 || ct1 != ct2 || cw1 != cw2 || ch1 != ch2) {
-        let cr1: number = cl1 + cw1 - 1;
-        let cb1: number = ct1 + ch1 - 1;
+        const cr1: number = cl1 + cw1 - 1;
+        const cb1: number = ct1 + ch1 - 1;
 
-        let cr2: number = cl2 + cw2 - 1;
-        let cb2: number = ct2 + ch2 - 1;
+        const cr2: number = cl2 + cw2 - 1;
+        const cb2: number = ct2 + ch2 - 1;
 
         let cyOut: boolean;
 
@@ -603,7 +630,7 @@ export class World {
         }
       }
 
-      const rect: Rect = this.rects[itemID];
+      const rect: IRect = this.rects[itemID];
 
       rect.x = x2;
       rect.y = y2;
@@ -618,7 +645,7 @@ export class World {
     goalY: number,
     filter?: (...args: any[]) => any
   ): { x: number; y: number; collisions: Collision[] } {
-    let { x, y, collisions } = this.check(itemID, goalX, goalY, filter);
+    const { x, y, collisions } = this.check(itemID, goalX, goalY, filter);
 
     this.update(itemID, x, y);
 
@@ -644,7 +671,7 @@ export class World {
 
     let detectedCollisions: Collision[] = [];
 
-    let itemRect: Rect = this.getRect(itemID);
+    const itemRect: IRect = this.getRect(itemID);
 
     // this is returning an empty array. WHY?
     let projectedCollisions: Collision[] = this.project(
@@ -661,13 +688,13 @@ export class World {
     let collisionsCounter: number = projectedCollisions?.length || 0;
 
     while (collisionsCounter > 0) {
-      let collision: any = projectedCollisions[0];
+      const collision: Collision = projectedCollisions[0];
 
       detectedCollisions.push(collision);
 
       visited[collision.other] = true;
 
-      let response = this.getResponseByName(collision.type);
+      let response = this.getResponseByName(collision.type!);
 
       const { x, y, collisions } = response(
         this,
@@ -700,7 +727,7 @@ const bump = {
 
     assertIsPositiveNumber(cellSize, 'cellSize');
 
-    let world = new World({
+    const world: World = new World({
       cellSize: cellSize,
       rects: {},
       rows: [],
@@ -732,4 +759,4 @@ const bump = {
   },
 };
 
-export default Object.seal(bump);
+export default Object.freeze(bump);
diff --git a/src/rect.ts b/src/rect.ts
index 7c1985f..8200dc7 100644
--- a/src/rect.ts
+++ b/src/rect.ts
@@ -1,4 +1,4 @@
-import { Collision, Coords, Rect } from '.';
+import { Collision, ICoords, IRect } from '.';
 import { DELTA } from './constants';
 import nearest from './helpers/generic/nearest';
 
@@ -9,7 +9,7 @@ export function rect_getNearestCorner(
   h: number,
   px: number,
   py: number
-): Coords {
+): ICoords {
   return { x: nearest(px, x, x + w), y: nearest(py, y, y + h) };
 }
 
@@ -133,7 +133,7 @@ export function rect_getDiff(
   y2: number,
   w2: number,
   h2: number
-): Rect {
+): IRect {
   return {
     x: x2 - x1 - w1,
     y: y2 - y1 - h1,
diff --git a/yarn.lock b/yarn.lock
index 8ccb07d..034dba9 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -7891,11 +7891,16 @@ tslib@^1.8.1, tslib@^1.9.0, tslib@^1.9.3:
   resolved "https://registry.yarnpkg.com/tslib/-/tslib-1.14.1.tgz#cf2d38bdc34a134bcaf1091c41f6619e2f672d00"
   integrity sha512-Xni35NKzjgMrwevysHTCArtLDpPvye8zV/0E4EyYn43P7/7qvQwPh9BGkHewbMulVntbigmcT7rdX3BNo9wRJg==
 
-tslib@^2.0.3, tslib@^2.3.0:
+tslib@^2.0.3:
   version "2.3.0"
   resolved "https://registry.yarnpkg.com/tslib/-/tslib-2.3.0.tgz#803b8cdab3e12ba581a4ca41c8839bbb0dacb09e"
   integrity sha512-N82ooyxVNm6h1riLCoyS9e3fuJ3AMG2zIZs2Gd1ATcSFjSA23Q0fzjjZeh0jbJvWVDZ0cJT8yaNNaaXHzueNjg==
 
+tslib@^2.3.1:
+  version "2.3.1"
+  resolved "https://registry.yarnpkg.com/tslib/-/tslib-2.3.1.tgz#e8a335add5ceae51aa261d32a490158ef042ef01"
+  integrity sha512-77EbyPPpMz+FRFRuAFlWMtmgUWGe9UOG2Z25NqCwiIjRhOf5iKGuzSe5P2w1laq+FkRy4p+PCuVkJSGkzTEKVw==
+
 tsutils@^3.17.1:
   version "3.21.0"
   resolved "https://registry.yarnpkg.com/tsutils/-/tsutils-3.21.0.tgz#b48717d394cea6c1e096983eed58e9d61715b623"
@@ -7964,10 +7969,10 @@ typescript@^3.7.3:
   resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.9.10.tgz#70f3910ac7a51ed6bef79da7800690b19bf778b8"
   integrity sha512-w6fIxVE/H1PkLKcCPsFqKE7Kv7QUwhU8qQY2MueZXWx5cPZdwFupLgKK3vntcK98BtNHZtAF4LA/yl2a7k8R6Q==
 
-typescript@^4.3.5:
-  version "4.3.5"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-4.3.5.tgz#4d1c37cc16e893973c45a06886b7113234f119f4"
-  integrity sha512-DqQgihaQ9cUrskJo9kIyW/+g0Vxsk8cDtZ52a3NGh0YNTfpUSArXSohyUGnvbPazEPLu398C0UxmKSOrPumUzA==
+typescript@^4.6.3:
+  version "4.6.3"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-4.6.3.tgz#eefeafa6afdd31d725584c67a0eaba80f6fc6c6c"
+  integrity sha512-yNIatDa5iaofVozS/uQJEl3JRWLKKGJKh6Yaiv0GLGSuhpFJe7P3SbHZ8/yjAHRQwKRoA6YZqlfjXWmVzoVSMw==
 
 unbox-primitive@^1.0.1:
   version "1.0.1"