diff --git a/build.gradle.kts b/build.gradle.kts
index d1e1f90..a93a69e 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -1,35 +1,99 @@
+import ru.landgrafhomyak.kotlin.kmp_gradle_build_helper.configureAllCompilationsOnAllTargets
+import ru.landgrafhomyak.kotlin.kmp_gradle_build_helper.configureAllCompilersOptionsOnAllTargets
 import ru.landgrafhomyak.kotlin.kmp_gradle_build_helper.defineAllMultiplatformTargets
 import ru.landgrafhomyak.kotlin.kmp_gradle_build_helper.defineXomrkGiteaMavenRepo
 
 buildscript {
-    repositories {
-        mavenCentral()
-        maven("https://maven.landgrafhomyak.ru/")
-    }
+	repositories {
+		mavenCentral()
+		maven("https://maven.landgrafhomyak.ru/")
+	}
 
-    dependencies {
-        classpath("ru.landgrafhomyak.kotlin:kotlin-mpp-gradle-build-helper:v0.3k2.1.10")
-    }
+	dependencies {
+		classpath("ru.landgrafhomyak.kotlin:kotlin-mpp-gradle-build-helper:v0.3k2.1.10")
+	}
 }
 
 plugins {
-    kotlin("multiplatform") version "2.2.10"
-    `maven-publish`
+	kotlin("multiplatform") version "2.2.10"
+	`maven-publish`
 }
 
 group = "ru.landgrafhomyak.multitasking"
 version = "1.0-SNAPSHOT"
 
 repositories {
-    mavenCentral()
+	mavenCentral()
 }
 
 kotlin {
-    defineAllMultiplatformTargets()
+	explicitApi()
+
+	jvm()
+	mingwX64()
+	linuxX64()
+	linuxArm64()
+	macosX64()
+	macosArm64()
+	js {
+		browser()
+		nodejs()
+	}
+
+
+	configureAllCompilersOptionsOnAllTargets {
+		freeCompilerArgs.addAll("-Xexpect-actual-classes")
+	}
+
+	jvm().compilations.configureEach {
+		compileTaskProvider {
+			compilerOptions {
+				freeCompilerArgs.addAll("-Xjvm-default=all", "-Xdirect-java-actualization")
+			}
+		}
+	}
+
+	sourceSets {
+		val commonMain by getting
+		val commonTest by getting
+
+		val notJvmMain by creating { dependsOn(commonMain) }
+		val notJvmTest by creating { dependsOn(commonTest) }
+
+		val multithreadPlatformMain by creating { dependsOn(commonMain) }
+		val multithreadPlatformTest by creating { dependsOn(commonTest) }
+		val singleThreadPlatformMain by creating { dependsOn(commonMain) }
+		val singleThreadPlatformTest by creating { dependsOn(commonTest) }
+
+		targets.configureEach target@{
+			if (this@target in setOf(this@kotlin.metadata(), this@kotlin.jvm()))
+				return@target
+
+			this@target.compilations.getByName("main").defaultSourceSet.dependsOn(notJvmMain)
+			this@target.compilations.getByName("test").defaultSourceSet.dependsOn(notJvmTest)
+		}
+
+		targets.configureEach target@{
+			if (this@target == this@kotlin.metadata())
+				return@target
+			if (this@target in setOf(this@kotlin.js())) {
+				this@target.compilations.getByName("main").defaultSourceSet.dependsOn(singleThreadPlatformMain)
+				this@target.compilations.getByName("test").defaultSourceSet.dependsOn(singleThreadPlatformTest)
+			} else {
+				this@target.compilations.getByName("main").defaultSourceSet.dependsOn(multithreadPlatformMain)
+				this@target.compilations.getByName("test").defaultSourceSet.dependsOn(multithreadPlatformTest)
+			}
+
+		}
+	}
+
+
+
+
 }
 
 publishing {
-    repositories {
-        defineXomrkGiteaMavenRepo()
-    }
+	repositories {
+		defineXomrkGiteaMavenRepo("Multitasking")
+	}
 }
\ No newline at end of file
diff --git a/settings.gradle.kts b/settings.gradle.kts
index 5b8c2f8..c502b5a 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -1,2 +1,2 @@
-rootProject.name = "multitasking-api"
+rootProject.name = "multitasking-core"
 
diff --git a/src/commonMain/kotlin/ru/landgrafhomyak/multitasking_0/Fiber.kt b/src/commonMain/kotlin/ru/landgrafhomyak/multitasking_0/Fiber.kt
new file mode 100644
index 0000000..8c2a42a
--- /dev/null
+++ b/src/commonMain/kotlin/ru/landgrafhomyak/multitasking_0/Fiber.kt
@@ -0,0 +1,31 @@
+package ru.landgrafhomyak.multitasking_0
+
+/**
+ * Handle of concurrency primitive with call stack saving.
+ */
+public interface Fiber {
+	/**
+	 * Returns [thread][Thread] to which fiber is bound if there are restrictions to threads where fiber can be [resumed][Fiber.resume].
+	 */
+	public val ownerThread: Thread?
+
+	/**
+	 * Returns `true` if this fiber running by any thread currently. Threadsafe getter.
+	 */
+	public val isRunning: Boolean /*get() = this.runningOnThread != null*/
+	/*public val runningOnThread: Thread?*/
+
+	/**
+	 * Switches execution flow back to thread or fiber called [resume()][Fiber.resume] to run this fiber.
+	 *
+	 * Must be called only inside fiber represented by this object.
+	 */
+	public fun yield()
+
+	/**
+	 * Switches execution flow of **current** [thread][Thread] or [fiber][Fiber] to this fiber until it's [return control back][Fiber.yield].
+	 *
+	 * If fiber [bound to any thread][Fiber.ownerThread], switching must be done only inside this thread or fibers running in this thread.
+	 */
+	public fun resume()
+}
\ No newline at end of file
diff --git a/src/commonMain/kotlin/ru/landgrafhomyak/multitasking_0/Thread.kt b/src/commonMain/kotlin/ru/landgrafhomyak/multitasking_0/Thread.kt
new file mode 100644
index 0000000..a83282e
--- /dev/null
+++ b/src/commonMain/kotlin/ru/landgrafhomyak/multitasking_0/Thread.kt
@@ -0,0 +1,12 @@
+package ru.landgrafhomyak.multitasking_0
+
+public expect class Thread {
+	public val name: String
+	override fun toString(): String
+
+	public var runningFiber: Fiber?
+
+	public companion object {
+		public fun getCurrentThread(): Thread
+	}
+}
\ No newline at end of file