diff --git a/tutorials/base64-library/build.gradle b/tutorials/base64-library/build.gradle
new file mode 100644
index 0000000000..3fbd6db1e1
--- /dev/null
+++ b/tutorials/base64-library/build.gradle
@@ -0,0 +1,58 @@
+plugins {
+    id 'kotlin-multiplatform' version '1.3.0-rc-116'
+}
+
+repositories {
+    maven { url 'http://dl.bintray.com/kotlin/kotlin-eap' }
+    mavenCentral()
+}
+
+apply plugin: 'maven-publish'
+group 'org.jetbrains.base64'
+version '1.0.0'
+
+kotlin {
+    targets {
+        fromPreset(presets.jvm, 'jvm')
+        fromPreset(presets.js, 'js')
+        fromPreset(presets.macosX64, 'macos')
+    }
+    sourceSets {
+        commonMain {
+            dependencies {
+                implementation 'org.jetbrains.kotlin:kotlin-stdlib-common'
+            }
+        }
+        commonTest {
+            dependencies {
+                implementation 'org.jetbrains.kotlin:kotlin-test-common'
+                implementation 'org.jetbrains.kotlin:kotlin-test-annotations-common'
+            }
+        }
+        jvmMain {
+            dependencies {
+                implementation 'org.jetbrains.kotlin:kotlin-stdlib-jdk8'
+            }
+        }
+        jvmTest {
+            dependencies {
+                implementation 'org.jetbrains.kotlin:kotlin-test'
+                implementation 'org.jetbrains.kotlin:kotlin-test-junit'
+            }
+        }
+        jsMain {
+            dependencies {
+                implementation 'org.jetbrains.kotlin:kotlin-stdlib-js'
+            }
+        }
+        jsTest {
+            dependencies {
+                implementation 'org.jetbrains.kotlin:kotlin-test-js'
+            }
+        }
+        macosMain {
+        }
+        macosTest {
+        }
+    }
+}
\ No newline at end of file
diff --git a/tutorials/base64-library/gradle.properties b/tutorials/base64-library/gradle.properties
new file mode 100644
index 0000000000..29e08e8ca8
--- /dev/null
+++ b/tutorials/base64-library/gradle.properties
@@ -0,0 +1 @@
+kotlin.code.style=official
\ No newline at end of file
diff --git a/tutorials/base64-library/gradle/wrapper/gradle-wrapper.jar b/tutorials/base64-library/gradle/wrapper/gradle-wrapper.jar
new file mode 100644
index 0000000000..91ca28c8b8
Binary files /dev/null and b/tutorials/base64-library/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/tutorials/base64-library/gradle/wrapper/gradle-wrapper.properties b/tutorials/base64-library/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 0000000000..c2b685fdb0
--- /dev/null
+++ b/tutorials/base64-library/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.7-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
\ No newline at end of file
diff --git a/tutorials/base64-library/gradlew b/tutorials/base64-library/gradlew
new file mode 100755
index 0000000000..cccdd3d517
--- /dev/null
+++ b/tutorials/base64-library/gradlew
@@ -0,0 +1,172 @@
+#!/usr/bin/env sh
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS=""
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=$(save "$@")
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"
diff --git a/tutorials/base64-library/settings.gradle b/tutorials/base64-library/settings.gradle
new file mode 100644
index 0000000000..b435ecbb24
--- /dev/null
+++ b/tutorials/base64-library/settings.gradle
@@ -0,0 +1,19 @@
+pluginManagement {
+    resolutionStrategy {
+        eachPlugin {
+            if (requested.id.id == "kotlin-multiplatform") {
+                useModule("org.jetbrains.kotlin:kotlin-gradle-plugin:${requested.version}")
+            }
+        }
+    }
+
+    repositories {
+        maven { url 'http://dl.bintray.com/kotlin/kotlin-eap' }
+        maven { url 'https://dl.bintray.com/kotlin/kotlin-eap' }
+        mavenCentral()
+
+        maven { url 'https://plugins.gradle.org/m2/' }
+    }
+}
+rootProject.name = 'base64-library'
+enableFeaturePreview('GRADLE_METADATA')
diff --git a/tutorials/base64-library/src/commonMain/kotlin/org/jetbrains/base64/Base64.kt b/tutorials/base64-library/src/commonMain/kotlin/org/jetbrains/base64/Base64.kt
new file mode 100644
index 0000000000..b5b13249bd
--- /dev/null
+++ b/tutorials/base64-library/src/commonMain/kotlin/org/jetbrains/base64/Base64.kt
@@ -0,0 +1,22 @@
+package org.jetbrains.base64
+
+/**
+ * Encoder interface which can encode byte arrays to Base64 format.
+ */
+interface Base64Encoder {
+    fun encode(src: ByteArray): ByteArray
+
+    fun encodeToString(src: ByteArray): String {
+        val encoded = encode(src)
+        return buildString(encoded.size) {
+            encoded.forEach { append(it.toChar()) }
+        }
+    }
+}
+
+expect object Base64Factory {
+    /**
+     * Creates a new instance of [Base64Encoder]
+     */
+    fun createEncoder(): Base64Encoder
+}
diff --git a/tutorials/base64-library/src/commonTest/kotlin/org/jetbrains/base64/Base64Test.kt b/tutorials/base64-library/src/commonTest/kotlin/org/jetbrains/base64/Base64Test.kt
new file mode 100644
index 0000000000..9d1426f3bf
--- /dev/null
+++ b/tutorials/base64-library/src/commonTest/kotlin/org/jetbrains/base64/Base64Test.kt
@@ -0,0 +1,29 @@
+package org.jetbrains.base64
+
+import kotlin.test.*
+
+class Base64Test {
+
+    @Test
+    fun testEncodeToString() {
+        checkEncodeToString("Kotlin is awesome", "S290bGluIGlzIGF3ZXNvbWU=")
+    }
+
+    @Test
+    fun testPaddedStrings() {
+        checkEncodeToString("", "")
+        checkEncodeToString("1", "MQ==")
+        checkEncodeToString("22", "MjI=")
+        checkEncodeToString("333", "MzMz")
+        checkEncodeToString("4444", "NDQ0NA==")
+
+    }
+
+    private fun checkEncodeToString(input: String, expectedOutput: String) {
+        assertEquals(expectedOutput, Base64Factory.createEncoder().encodeToString(input.asciiToByteArray()))
+    }
+
+    private fun String.asciiToByteArray() = ByteArray(length) {
+        get(it).toByte()
+    }
+}
diff --git a/tutorials/base64-library/src/jsMain/kotlin/org/jetbrains/base64/Base64.kt b/tutorials/base64-library/src/jsMain/kotlin/org/jetbrains/base64/Base64.kt
new file mode 100644
index 0000000000..40a7dc2754
--- /dev/null
+++ b/tutorials/base64-library/src/jsMain/kotlin/org/jetbrains/base64/Base64.kt
@@ -0,0 +1,17 @@
+package org.jetbrains.base64
+
+actual object Base64Factory {
+    actual fun createEncoder(): Base64Encoder = JsBase64Encoder
+}
+
+object JsBase64Encoder : Base64Encoder {
+    override fun encode(src: ByteArray): ByteArray {
+        val buffer = js("Buffer").from(src)
+        val string = buffer.toString("base64") as String
+        return ByteArray(string.length) { string[it].toByte() }
+    }
+}
+
+fun main(args: Array<String>) {
+    println(JsBase64Encoder.encodeToString(byteArrayOf(75, 111, 116, 108, 105, 110)))
+}
diff --git a/tutorials/base64-library/src/jvmMain/kotlin/org/jetbrains/base64/Base64.kt b/tutorials/base64-library/src/jvmMain/kotlin/org/jetbrains/base64/Base64.kt
new file mode 100644
index 0000000000..dea5eff543
--- /dev/null
+++ b/tutorials/base64-library/src/jvmMain/kotlin/org/jetbrains/base64/Base64.kt
@@ -0,0 +1,12 @@
+package org.jetbrains.base64
+
+import java.util.*
+
+actual object Base64Factory {
+    actual fun createEncoder(): Base64Encoder = JvmBase64Encoder
+}
+
+object JvmBase64Encoder : Base64Encoder {
+    override fun encode(src: ByteArray): ByteArray = Base64.getEncoder().encode(src)
+    override fun encodeToString(src: ByteArray): String = Base64.getEncoder().encodeToString(src)
+}
diff --git a/tutorials/base64-library/src/jvmTest/kotlin/org/jetbrains/base64/Base64JvmTest.kt b/tutorials/base64-library/src/jvmTest/kotlin/org/jetbrains/base64/Base64JvmTest.kt
new file mode 100644
index 0000000000..4b90d89651
--- /dev/null
+++ b/tutorials/base64-library/src/jvmTest/kotlin/org/jetbrains/base64/Base64JvmTest.kt
@@ -0,0 +1,14 @@
+package org.jetbrains.base64
+
+import org.junit.Test
+import kotlin.test.*
+
+class Base64JvmTest {
+
+    @Test
+    fun testNonAsciiString() {
+        val utf8String = "Gödel"
+        val actual = Base64Factory.createEncoder().encodeToString(utf8String.toByteArray())
+        assertEquals("R8O2ZGVs", actual)
+    }
+}
\ No newline at end of file
diff --git a/tutorials/base64-library/src/macosMain/kotlin/base64/Base64.kt b/tutorials/base64-library/src/macosMain/kotlin/base64/Base64.kt
new file mode 100644
index 0000000000..e7239baf95
--- /dev/null
+++ b/tutorials/base64-library/src/macosMain/kotlin/base64/Base64.kt
@@ -0,0 +1,39 @@
+package org.jetbrains.base64
+
+private val BASE64_ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+private val BASE64_MASK: Byte = 0x3f
+private val BASE64_PAD = '='
+
+private val BASE64_INVERSE_ALPHABET = IntArray(256) {
+    BASE64_ALPHABET.indexOf(it.toChar())
+}
+
+private fun Int.toBase64(): Char = BASE64_ALPHABET[this]
+
+actual object Base64Factory {
+    actual fun createEncoder(): Base64Encoder = NativeBase64Encoder
+}
+
+object NativeBase64Encoder : Base64Encoder {
+    override fun encode(src: ByteArray): ByteArray {
+        fun ByteArray.getOrZero(index: Int): Int = if (index >= size) 0 else get(index).toInt()
+
+        val result = ArrayList<Byte>(4 * src.size / 3)
+        var index = 0
+        while (index < src.size) {
+            val symbolsLeft = src.size - index
+            val padSize = if (symbolsLeft >= 3) 0 else (3 - symbolsLeft) * 8 / 6
+            val chunk = (src.getOrZero(index) shl 16) or (src.getOrZero(index + 1) shl 8) or src.getOrZero(index + 2)
+            index += 3
+
+            for (i in 3 downTo padSize) {
+                val char = (chunk shr (6 * i)) and BASE64_MASK.toInt()
+                result.add(char.toBase64().toByte())
+            }
+
+            repeat(padSize) { result.add(BASE64_PAD.toByte()) }
+        }
+
+        return result.toByteArray()
+    }
+}