diff --git a/libs/microbit/core.d.ts b/libs/microbit/core.d.ts
deleted file mode 100644
index 0f7f7f96..00000000
--- a/libs/microbit/core.d.ts
+++ /dev/null
@@ -1,181 +0,0 @@
-/// <reference no-default-lib="true"/>
-
-interface Array<T> {
-    /**
-      * Gets or sets the length of the array. This is a number one higher than the highest element defined in an array.
-      */
-    //% shim=Array_::length
-    length: number;
-
-    /**
-      * Appends new elements to an array.
-      * @param items New elements of the Array.
-      */
-    //% shim=Array_::push
-    push(item: T): void;
-    
-    /**
-      * Removes the last element from an array and returns it.
-      */
-    //% helper=arrayPop
-    pop(): T;
-
-    /**
-      * Reverses the elements in an Array. 
-      */
-    //% helper=arrayReverse
-    reverse(): void;
-    
-    /**
-      * Removes the first element from an array and returns it.
-      */
-    //% helper=arrayShift
-    shift(): T;
-    
-    /** 
-      * Returns a section of an array.
-      * @param start The beginning of the specified portion of the array.
-      * @param end The end of the specified portion of the array.
-      */
-    //% helper=arraySlice
-    slice(start: number, end: number): T[];
-
-    /** Removes the first occurence of an object. Returns true if removed. */
-    //% shim=Array_::removeElement
-    removeElement(element:T) : boolean;
-    
-    /** Removes the object at position index. */
-    //% shim=Array_::removeAt
-    removeAt(idx:number) : void;
-    
-    
-    /**
-      * Removes elements from an array.
-      * @param start The zero-based location in the array from which to start removing elements.
-      * @param deleteCount The number of elements to remove.
-      */
-    //% helper=arraySplice
-    splice(start: number, deleteCount: number): void;
-
-    /**
-      * Inserts new elements at the start of an array.
-      * @param items  Elements to insert at the start of the Array.
-      */
-    //% helper=arrayUnshift
-    unshift(item:T): void;
-
-    /**
-      * Returns the index of the first occurrence of a value in an array.
-      * @param searchElement The value to locate in the array.
-      * @param fromIndex The array index at which to begin the search. If fromIndex is omitted, the search starts at index 0.
-      */
-    //% shim=Array_::indexOf
-    indexOf(searchElement: T, fromIndex?: number): number;
-
-
-    [n: number]: T;
-}
-
-declare interface String {
-    /**
-     * Returns the character at the specified index.
-     * @param pos The zero-based index of the desired character.
-     */
-    //% shim=String_::charAt
-    charAt(pos: number): string;
-
-    /** 
-     * Returns the Unicode value of the character at the specified location.
-     * @param index The zero-based index of the desired character. If there is no character at the specified index, NaN is returned.
-     */
-    //% shim=String_::charCodeAt
-    charCodeAt(index: number): number;
-
-    /**
-     * Returns a string that contains the concatenation of two or more strings.
-     * @param other The string to append to the end of the string.  
-     */
-    //% shim=String_::concat
-    concat(other: string): string;
-
-    /**
-     * Determines whether relative order of two strings (in ASCII encoding).
-     * @param that String to compare to target string
-     */
-    //% shim=String_::compare
-    compare(that: string): number;
-
-    /** Returns the length of a String object. */
-    //% property shim=String_::length
-    length: number;
-
-    [index: number]: string;
-}
-
-
-
-/**
-  * Converts A string to an integer.
-  * @param s A string to convert into a number.
-  */
-//% shim=String_::toNumber
-declare function parseInt(s: string): number;
-
-interface Object {}
-interface Function {}
-interface IArguments {}
-interface RegExp {}
-
-
-declare interface Boolean {
-    /**
-     * Returns a string representation of an object.
-     */
-    //% shim=Boolean_::toString
-    toString(): string;
-}
-
-declare namespace String {
-
-    /**
-     * Make a string from the given ASCII character code. 
-     */
-    //% shim=String_::fromCharCode
-    function fromCharCode(code: number): string;
-}
-
-
-declare interface Number {
-    /**
-     * Returns a string representation of a number.
-     */
-    //% shim=Number_::toString
-    toString(): string;
-}
-
-/**
- * Numbers and arithmetic operators
- */
-declare namespace Math {
-
-    /**
-     * Returns the value of a base expression taken to a specified power. 
-     * @param x The base value of the expression.
-     * @param y The exponent value of the expression.
-     */
-    //% shim=Math_::pow
-    function pow(x: number, y: number): number;
-
-    /** 
-     * Returns a pseudorandom number between 0 and `max`. 
-     */
-    //% shim=Math_::random
-    function random(max: number): number;
-
-    /**
-     * Returns the square root of a number.
-     * @param x A numeric expression.
-     */
-    //% shim=Math_::sqrt
-    function sqrt(x: number): number;
-}