diff --git a/README.md b/README.md
index fac874d..514acf1 100644
--- a/README.md
+++ b/README.md
@@ -8,6 +8,11 @@ Check our [User's Manual](https://c64lib.github.io/user-manual/#_common) for mor
 
 ## Change log
 
+### Changes in version 0.4.0
+
+* New macro: `compress.asm\compressRLE`.
+* New subroutine: `decompress_rle.asm`.
+
 ### Changes in version 0.3.0
 
 * New macro: `math.asm/mulAndAdd` - multiple two numbers and add result to memory location.
diff --git a/build.gradle b/build.gradle
index 5c7d3b3..fee8260 100644
--- a/build.gradle
+++ b/build.gradle
@@ -28,7 +28,7 @@ retroProject {
     dialect = "KickAssembler"
     dialectVersion = "5.25"
     libDirs = [".ra/deps/c64lib"]
-    verbose = true
+    srcDirs = ["lib"]
     libFromGitHub "c64lib/64spec", "0.7.0pr"
 }
 
diff --git a/lib/common-global.asm b/lib/common-global.asm
index 8e38fd6..00c8f5d 100644
--- a/lib/common-global.asm
+++ b/lib/common-global.asm
@@ -23,6 +23,8 @@
  * SOFTWARE.
  */
 #import "common.asm"
+#importonce
+
 .filenamespace c64lib
 
 .macro @c64lib_ch(data) { ch(data) }
diff --git a/lib/compress-global.asm b/lib/compress-global.asm
new file mode 100644
index 0000000..5c8de07
--- /dev/null
+++ b/lib/compress-global.asm
@@ -0,0 +1,30 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2017-2023 c64lib
+ * Copyright (c) 2017-2023 Maciej Małecki
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#import "compress.asm"
+#importonce
+
+.filenamespace c64lib
+
+.macro @c64lib_compressRLE(data) { compressRLE(data) }
diff --git a/lib/compress.asm b/lib/compress.asm
new file mode 100644
index 0000000..ef03ca3
--- /dev/null
+++ b/lib/compress.asm
@@ -0,0 +1,55 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2017-2023 c64lib
+ * Copyright (c) 2017-2023 Maciej Małecki
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#importonce
+.filenamespace c64lib
+
+/*
+ * Performs RLE (Running Length Encoding) compression of given binary data (kick assembler data type).
+ * The compressed result is placed as is in the result file starting from the place where this macro is called.
+ */
+.macro compressRLE(binaryData) {
+    .var runLength = 0
+    .var runValue = 0
+    .var crunchedLength = 0
+    .for(var i = 0; i < binaryData.getSize(); i++) {
+        .if(runLength > 0 && (binaryData.get(i) != runValue || runLength == $ff)) {
+            .byte runLength
+            .byte runValue
+            .eval runLength = 0
+            .eval crunchedLength = crunchedLength + 2
+        }
+        .if(runLength == 0) {
+            .eval runValue = binaryData.get(i)
+            .eval runLength = 1
+        } else {
+            .eval runLength++
+        }
+    }
+    .byte runLength
+    .byte runValue
+    .byte $00 // end mark
+    .eval crunchedLength++
+    .print "Crunched from " + binaryData.getSize() + " to " + crunchedLength + " (" + round((crunchedLength/binaryData.getSize())*100) + "%)"
+}
diff --git a/lib/sub/decompress-rle.asm b/lib/sub/decompress-rle.asm
new file mode 100644
index 0000000..2584c8e
--- /dev/null
+++ b/lib/sub/decompress-rle.asm
@@ -0,0 +1,68 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2017-2023 c64lib
+ * Copyright (c) 2017-2023 Maciej Małecki
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#import "../invoke.asm"
+
+.namespace c64lib {
+
+    /*
+    * Stack:
+    *   source address (2 bytes)
+    *   dest address (2 bytes)
+    */
+    decompressRLE: {
+    invokeStackBegin(returnPtr)
+    pullParamW(destination)
+    pullParamW(source)
+    invokeStackEnd(returnPtr)
+
+    nextSequence:
+        jsr loadSource
+        cmp #0
+        beq end // end mark
+        tax // x <- run length
+        jsr loadSource // a <- run value
+        decrunch:
+        sta destination:$ffff
+        inc destination
+        bne !+
+            inc destination + 1
+        !:
+        dex
+        bne decrunch
+    jmp nextSequence
+
+    end:
+    rts
+    loadSource:
+        lda source:$ffff
+        inc source
+        bne !+
+        inc source + 1
+        !:
+        rts
+    // locals
+    returnPtr: .word 0
+    }
+}
\ No newline at end of file
diff --git a/spec/decompress-rle.spec.asm b/spec/decompress-rle.spec.asm
new file mode 100644
index 0000000..f0f045d
--- /dev/null
+++ b/spec/decompress-rle.spec.asm
@@ -0,0 +1,57 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2017-2023 c64lib
+ * Copyright (c) 2017-2023 Maciej Małecki
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#import "64spec/lib/64spec.asm"
+#import "../lib/compress-global.asm"
+#import "../lib/invoke-global.asm"
+
+.var testData = LoadBinary("decompress-rle.test-data.txt")
+
+sfspec: init_spec()
+    describe("decompressRLE")
+
+    it("decompress data"); {
+        c64lib_pushParamW(compressedData)
+        c64lib_pushParamW(targetData)
+        jsr decompressRLE
+
+        assert_bytes_equal testData.getSize(): targetData: originalData
+    }
+finish_spec()
+
+* = * "Data"
+decompressRLE:
+    #import "../lib/sub/decompress-rle.asm"
+
+originalData:
+    .fill testData.getSize(), testData.get(i)
+originalDataEnd:
+
+compressedData:
+    c64lib_compressRLE(testData)
+compressedDataEnd:
+
+targetData:
+    .fill testData.getSize(), 0
+targetDataEnd:
diff --git a/spec/decompress-rle.test-data.txt b/spec/decompress-rle.test-data.txt
new file mode 100644
index 0000000..74f02ac
--- /dev/null
+++ b/spec/decompress-rle.test-data.txt
@@ -0,0 +1 @@
+wegiel drogi to i atari nie dziala
\ No newline at end of file