diff --git a/internal/preproc/preproc.go b/internal/preproc/preproc.go
index 081e243..025fb7e 100644
--- a/internal/preproc/preproc.go
+++ b/internal/preproc/preproc.go
@@ -3,17 +3,24 @@ package preproc
 import (
 	"fmt"
 	"path/filepath"
-
-	//"path/filepath"
 	"strings"
 )
 
+type LineKind int
+
+const (
+	Source LineKind = iota
+	Assembler
+	Script
+)
+
 // Line represents one post-processed source line and its provenance.
 type Line struct {
-	Text           string   // post-preprocessor line text (after define replacement)
+	RawText        string   // original line text before any processing
+	Text           string   // post-preprocessor line text (after define replacement, comment stripping)
 	Filename       string   // file the line came from (after resolving includes)
 	LineNo         int      // 1-based line number in Filename
-	Tokens         []string // whitespace-split tokens from Text (space or tab; consecutive collapsed)
+	Kind           LineKind // Source, Assembler, or Script
 	PragmaSetIndex int      // index into Pragma stack for this line
 }
 
@@ -38,20 +45,22 @@ func PreProcess(rootFilename string, reader ...FileReader) ([]Line, error) {
 // -------------------- internal --------------------
 
 type preproc struct {
-	defs   *DefineList // from definelist.go
-	pragma *Pragma     // pragma handler
-	cond   []bool      // conditional stack; a line is active if all are true
-	inAsm  bool        // true when inside ASM/ENDASM block
-	reader FileReader  // file reader abstraction
+	defs     *DefineList // from definelist.go
+	pragma   *Pragma     // pragma handler
+	cond     []bool      // conditional stack; a line is active if all are true
+	inAsm    bool        // true when inside ASM/ENDASM block
+	inScript bool        // true when inside SCRIPT/ENDSCRIPT block
+	reader   FileReader  // file reader abstraction
 }
 
 func newPreproc(reader FileReader) *preproc {
 	return &preproc{
-		defs:   NewDefineList(),
-		pragma: NewPragma(),
-		cond:   []bool{},
-		inAsm:  false,
-		reader: reader,
+		defs:     NewDefineList(),
+		pragma:   NewPragma(),
+		cond:     []bool{},
+		inAsm:    false,
+		inScript: false,
+		reader:   reader,
 	}
 }
 
@@ -106,39 +115,48 @@ func (p *preproc) run(root string) ([]Line, error) {
 		tokens := strings.Fields(raw)
 
 		// ASM mode handling
-		if !p.inAsm {
+		if !p.inAsm && !p.inScript {
 			// Check for ASM entry
 			if includeSource && len(tokens) > 0 && tokens[0] == "ASM" {
 				p.inAsm = true
-				out = append(out, Line{
-					Text:           raw,
-					Filename:       currFrame.path,
-					LineNo:         currFrame.line,
-					Tokens:         []string{},
-					PragmaSetIndex: p.pragma.GetCurrentPragmaSetIndex(),
-				})
-				continue
+				continue // don't emit ASM marker
 			}
-		} else {
+			// Check for SCRIPT entry
+			if includeSource && len(tokens) > 0 && tokens[0] == "SCRIPT" {
+				p.inScript = true
+				continue // don't emit SCRIPT marker
+			}
+		} else if p.inAsm {
 			// We're in ASM mode
 			// Check for ENDASM
 			if len(tokens) > 0 && tokens[0] == "ENDASM" {
 				p.inAsm = false
-				out = append(out, Line{
-					Text:           raw,
-					Filename:       currFrame.path,
-					LineNo:         currFrame.line,
-					Tokens:         []string{},
-					PragmaSetIndex: p.pragma.GetCurrentPragmaSetIndex(),
-				})
-				continue
+				continue // don't emit ENDASM marker
 			}
-			// Otherwise emit line verbatim
+			// Otherwise emit line verbatim as Assembler
 			out = append(out, Line{
+				RawText:        raw,
 				Text:           raw,
 				Filename:       currFrame.path,
 				LineNo:         currFrame.line,
-				Tokens:         []string{},
+				Kind:           Assembler,
+				PragmaSetIndex: p.pragma.GetCurrentPragmaSetIndex(),
+			})
+			continue
+		} else if p.inScript {
+			// We're in SCRIPT mode
+			// Check for ENDSCRIPT
+			if len(tokens) > 0 && tokens[0] == "ENDSCRIPT" {
+				p.inScript = false
+				continue // don't emit ENDSCRIPT marker
+			}
+			// Otherwise emit line verbatim as Script
+			out = append(out, Line{
+				RawText:        raw,
+				Text:           raw,
+				Filename:       currFrame.path,
+				LineNo:         currFrame.line,
+				Kind:           Script,
 				PragmaSetIndex: p.pragma.GetCurrentPragmaSetIndex(),
 			})
 			continue
@@ -239,13 +257,21 @@ func (p *preproc) run(root string) ([]Line, error) {
 			continue
 		}
 
-		// Non-directive: expand defines and emit.
+		// Non-directive Source line: expand defines, strip comments, emit
 		text := p.defs.ReplaceDefines(raw)
+
+		// Strip comments (everything after //)
+		if idx := strings.Index(text, "//"); idx >= 0 {
+			text = text[:idx]
+		}
+		text = strings.TrimRight(text, " \t")
+
 		out = append(out, Line{
+			RawText:        raw,
 			Text:           text,
 			Filename:       currFrame.path,
 			LineNo:         currFrame.line,
-			Tokens:         strings.Fields(text),
+			Kind:           Source,
 			PragmaSetIndex: p.pragma.GetCurrentPragmaSetIndex(),
 		})
 	}
diff --git a/internal/preproc/preproc_test.go b/internal/preproc/preproc_test.go
index 7e9a312..2427c55 100644
--- a/internal/preproc/preproc_test.go
+++ b/internal/preproc/preproc_test.go
@@ -26,6 +26,10 @@ func TestPreProcess_BasicDefine(t *testing.T) {
 	if lines[0].Text != "LDA #42" {
 		t.Errorf("expected 'LDA #42', got %q", lines[0].Text)
 	}
+
+	if lines[0].Kind != Source {
+		t.Errorf("expected Kind=Source, got %v", lines[0].Kind)
+	}
 }
 
 func TestPreProcess_DefineExpansion(t *testing.T) {
@@ -72,7 +76,6 @@ func TestPreProcess_IncludeGuard(t *testing.T) {
 		t.Fatalf("PreProcess failed: %v", err)
 	}
 
-	// First include emits LABEL, second include is blocked by guard
 	if len(lines) != 2 {
 		t.Fatalf("expected 2 lines, got %d", len(lines))
 	}
@@ -102,18 +105,254 @@ func TestPreProcess_ASMBlock(t *testing.T) {
 		t.Fatalf("PreProcess failed: %v", err)
 	}
 
-	if len(lines) != 5 {
-		t.Fatalf("expected 5 lines, got %d", len(lines))
+	// ASM and ENDASM markers are stripped, so only 2 asm lines + 1 source line
+	if len(lines) != 3 {
+		t.Fatalf("expected 3 lines, got %d", len(lines))
 	}
 
 	// ASM content should NOT be processed
-	if lines[1].Text != "  lda #FOO" {
-		t.Errorf("expected '  lda #FOO', got %q", lines[1].Text)
+	if lines[0].Text != "  lda #FOO" {
+		t.Errorf("expected '  lda #FOO', got %q", lines[0].Text)
+	}
+	if lines[0].Kind != Assembler {
+		t.Errorf("expected Kind=Assembler, got %v", lines[0].Kind)
+	}
+
+	if lines[1].Text != "  sta $d020" {
+		t.Errorf("expected '  sta $d020', got %q", lines[1].Text)
+	}
+	if lines[1].Kind != Assembler {
+		t.Errorf("expected Kind=Assembler, got %v", lines[1].Kind)
 	}
 
 	// After ENDASM, defines work again
-	if lines[4].Text != "LDA #42" {
-		t.Errorf("expected 'LDA #42', got %q", lines[4].Text)
+	if lines[2].Text != "LDA #42" {
+		t.Errorf("expected 'LDA #42', got %q", lines[2].Text)
+	}
+	if lines[2].Kind != Source {
+		t.Errorf("expected Kind=Source, got %v", lines[2].Kind)
+	}
+}
+
+func TestPreProcess_ScriptBlock(t *testing.T) {
+	files := map[string][]string{
+		"test.c65": {
+			"#DEFINE VAR = 100",
+			"SCRIPT",
+			"  x = VAR + 1",
+			"  print(x)",
+			"ENDSCRIPT",
+			"LDA #VAR",
+		},
+	}
+	reader := NewMockFileReader(files)
+	lines, err := PreProcess("test.c65", reader)
+	if err != nil {
+		t.Fatalf("PreProcess failed: %v", err)
+	}
+
+	// SCRIPT and ENDSCRIPT markers are stripped
+	if len(lines) != 3 {
+		t.Fatalf("expected 3 lines, got %d", len(lines))
+	}
+
+	// Script content should NOT be processed
+	if lines[0].Text != "  x = VAR + 1" {
+		t.Errorf("expected '  x = VAR + 1', got %q", lines[0].Text)
+	}
+	if lines[0].Kind != Script {
+		t.Errorf("expected Kind=Script, got %v", lines[0].Kind)
+	}
+
+	if lines[1].Text != "  print(x)" {
+		t.Errorf("expected '  print(x)', got %q", lines[1].Text)
+	}
+	if lines[1].Kind != Script {
+		t.Errorf("expected Kind=Script, got %v", lines[1].Kind)
+	}
+
+	// After ENDSCRIPT, defines work again
+	if lines[2].Text != "LDA #100" {
+		t.Errorf("expected 'LDA #100', got %q", lines[2].Text)
+	}
+	if lines[2].Kind != Source {
+		t.Errorf("expected Kind=Source, got %v", lines[2].Kind)
+	}
+}
+
+func TestPreProcess_CommentStripping(t *testing.T) {
+	files := map[string][]string{
+		"test.c65": {
+			"LDA #42 // load accumulator",
+			"STA $D020 // border color",
+			"NOP // comment only",
+			"JMP $0810",
+		},
+	}
+	reader := NewMockFileReader(files)
+	lines, err := PreProcess("test.c65", reader)
+	if err != nil {
+		t.Fatalf("PreProcess failed: %v", err)
+	}
+
+	if len(lines) != 4 {
+		t.Fatalf("expected 4 lines, got %d", len(lines))
+	}
+
+	if lines[0].Text != "LDA #42" {
+		t.Errorf("expected 'LDA #42', got %q", lines[0].Text)
+	}
+	if lines[0].RawText != "LDA #42 // load accumulator" {
+		t.Errorf("expected RawText to preserve comment, got %q", lines[0].RawText)
+	}
+
+	if lines[1].Text != "STA $D020" {
+		t.Errorf("expected 'STA $D020', got %q", lines[1].Text)
+	}
+
+	if lines[2].Text != "NOP" {
+		t.Errorf("expected 'NOP', got %q", lines[2].Text)
+	}
+
+	if lines[3].Text != "JMP $0810" {
+		t.Errorf("expected 'JMP $0810', got %q", lines[3].Text)
+	}
+}
+
+func TestPreProcess_CommentInASMBlock(t *testing.T) {
+	files := map[string][]string{
+		"test.c65": {
+			"ASM",
+			"  lda #42 // this comment stays",
+			"  sta $d020 // this too",
+			"ENDASM",
+		},
+	}
+	reader := NewMockFileReader(files)
+	lines, err := PreProcess("test.c65", reader)
+	if err != nil {
+		t.Fatalf("PreProcess failed: %v", err)
+	}
+
+	if len(lines) != 2 {
+		t.Fatalf("expected 2 lines, got %d", len(lines))
+	}
+
+	// Comments should be preserved in ASM blocks
+	if lines[0].Text != "  lda #42 // this comment stays" {
+		t.Errorf("expected comment preserved, got %q", lines[0].Text)
+	}
+	if lines[1].Text != "  sta $d020 // this too" {
+		t.Errorf("expected comment preserved, got %q", lines[1].Text)
+	}
+}
+
+func TestPreProcess_CommentInScriptBlock(t *testing.T) {
+	files := map[string][]string{
+		"test.c65": {
+			"SCRIPT",
+			"  x = 1 // script comment",
+			"  y = 2 // another one",
+			"ENDSCRIPT",
+		},
+	}
+	reader := NewMockFileReader(files)
+	lines, err := PreProcess("test.c65", reader)
+	if err != nil {
+		t.Fatalf("PreProcess failed: %v", err)
+	}
+
+	if len(lines) != 2 {
+		t.Fatalf("expected 2 lines, got %d", len(lines))
+	}
+
+	// Comments should be preserved in Script blocks
+	if lines[0].Text != "  x = 1 // script comment" {
+		t.Errorf("expected comment preserved, got %q", lines[0].Text)
+	}
+	if lines[1].Text != "  y = 2 // another one" {
+		t.Errorf("expected comment preserved, got %q", lines[1].Text)
+	}
+}
+
+func TestPreProcess_RawTextPreservation(t *testing.T) {
+	files := map[string][]string{
+		"test.c65": {
+			"#DEFINE FOO = 42",
+			"LDA #FOO // comment here",
+		},
+	}
+	reader := NewMockFileReader(files)
+	lines, err := PreProcess("test.c65", reader)
+	if err != nil {
+		t.Fatalf("PreProcess failed: %v", err)
+	}
+
+	if len(lines) != 1 {
+		t.Fatalf("expected 1 line, got %d", len(lines))
+	}
+
+	// RawText should be original
+	if lines[0].RawText != "LDA #FOO // comment here" {
+		t.Errorf("expected RawText 'LDA #FOO // comment here', got %q", lines[0].RawText)
+	}
+
+	// Text should be processed
+	if lines[0].Text != "LDA #42" {
+		t.Errorf("expected Text 'LDA #42', got %q", lines[0].Text)
+	}
+}
+
+func TestPreProcess_MismatchedBlockTerminators(t *testing.T) {
+	tests := []struct {
+		name  string
+		lines []string
+	}{
+		{
+			name: "ASM ended with ENDSCRIPT",
+			lines: []string{
+				"ASM",
+				"  lda #42",
+				"ENDSCRIPT",
+				"NOP",
+			},
+		},
+		{
+			name: "SCRIPT ended with ENDASM",
+			lines: []string{
+				"SCRIPT",
+				"  x = 1",
+				"ENDASM",
+				"NOP",
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			files := map[string][]string{
+				"test.c65": tt.lines,
+			}
+			reader := NewMockFileReader(files)
+			lines, err := PreProcess("test.c65", reader)
+			if err != nil {
+				t.Fatalf("PreProcess failed: %v", err)
+			}
+
+			// Wrong terminator won't close the block
+			// All lines including the wrong terminator should be in the block
+			if len(lines) < 2 {
+				t.Errorf("expected at least 2 lines, got %d", len(lines))
+			}
+
+			// The mismatched terminator should be treated as block content
+			// and NOP should still be in the block too
+			for _, line := range lines {
+				if line.Kind == Source {
+					t.Errorf("found Source line when all should be in block: %q", line.Text)
+				}
+			}
+		})
 	}
 }
 
@@ -295,7 +534,6 @@ func TestPreProcess_PragmaWithDefines(t *testing.T) {
 		t.Fatalf("PreProcess failed: %v", err)
 	}
 
-	// Pragma should have been processed with define expansion
 	if len(lines) != 1 {
 		t.Fatalf("expected 1 line, got %d", len(lines))
 	}
@@ -368,63 +606,6 @@ func TestPreProcess_ConditionalHalt(t *testing.T) {
 	}
 }
 
-func TestPreProcess_Tokens(t *testing.T) {
-	files := map[string][]string{
-		"test.c65": {
-			"LDA #$42",
-			"  STA   $D020  ",
-		},
-	}
-	reader := NewMockFileReader(files)
-	lines, err := PreProcess("test.c65", reader)
-	if err != nil {
-		t.Fatalf("PreProcess failed: %v", err)
-	}
-
-	expectedTokens := [][]string{
-		{"LDA", "#$42"},
-		{"STA", "$D020"},
-	}
-
-	for i, expected := range expectedTokens {
-		if len(lines[i].Tokens) != len(expected) {
-			t.Errorf("line %d: expected %d tokens, got %d", i, len(expected), len(lines[i].Tokens))
-			continue
-		}
-		for j, tok := range expected {
-			if lines[i].Tokens[j] != tok {
-				t.Errorf("line %d token %d: expected %q, got %q", i, j, tok, lines[i].Tokens[j])
-			}
-		}
-	}
-}
-
-func TestPreProcess_ASMTokens(t *testing.T) {
-	files := map[string][]string{
-		"test.c65": {
-			"ASM",
-			"  lda #$42",
-			"ENDASM",
-		},
-	}
-	reader := NewMockFileReader(files)
-	lines, err := PreProcess("test.c65", reader)
-	if err != nil {
-		t.Fatalf("PreProcess failed: %v", err)
-	}
-
-	// ASM and ENDASM have empty token arrays
-	if len(lines[0].Tokens) != 0 {
-		t.Errorf("ASM should have empty tokens, got %d", len(lines[0].Tokens))
-	}
-	if len(lines[1].Tokens) != 0 {
-		t.Errorf("ASM content should have empty tokens, got %d", len(lines[1].Tokens))
-	}
-	if len(lines[2].Tokens) != 0 {
-		t.Errorf("ENDASM should have empty tokens, got %d", len(lines[2].Tokens))
-	}
-}
-
 func TestPreProcess_ComplexIncludeGuard(t *testing.T) {
 	files := map[string][]string{
 		"c64scr.c65": {
@@ -452,7 +633,6 @@ func TestPreProcess_ComplexIncludeGuard(t *testing.T) {
 	}
 
 	// First include should emit the library, second should be blocked
-	// Count non-directive lines from first include
 	count := 0
 	for _, line := range lines {
 		if strings.Contains(line.Text, "lda $d011") {
@@ -461,7 +641,7 @@ func TestPreProcess_ComplexIncludeGuard(t *testing.T) {
 	}
 
 	if count != 1 {
-		t.Errorf("expected 1 lib lines from multiple includes of same file, got %d", count)
+		t.Errorf("expected 1 occurrence from multiple includes of same file, got %d", count)
 	}
 }
 
@@ -535,52 +715,6 @@ func TestPreProcess_FilenameAndLineNumberTracking(t *testing.T) {
 	}
 }
 
-func TestPreProcess_Tokenization(t *testing.T) {
-	files := map[string][]string{
-		"test.c65": {
-			"LDA #$42",                    // simple tokens
-			"  STA   $D020  ",             // leading/trailing whitespace, multiple spaces
-			"LET var = $1000",             // multiple tokens with =
-			"	JMP	$0810",                  // tabs
-			"  CALL  func  (  a  b  c  )", // spaces around everything
-			"",                            // empty line
-			"NOP",                         // single token
-		},
-	}
-	reader := NewMockFileReader(files)
-	lines, err := PreProcess("test.c65", reader)
-	if err != nil {
-		t.Fatalf("PreProcess failed: %v", err)
-	}
-
-	expected := [][]string{
-		{"LDA", "#$42"},
-		{"STA", "$D020"},
-		{"LET", "var", "=", "$1000"},
-		{"JMP", "$0810"},
-		{"CALL", "func", "(", "a", "b", "c", ")"},
-		{}, // empty line has no tokens
-		{"NOP"},
-	}
-
-	if len(lines) != len(expected) {
-		t.Fatalf("expected %d lines, got %d", len(expected), len(lines))
-	}
-
-	for i, exp := range expected {
-		if len(lines[i].Tokens) != len(exp) {
-			t.Errorf("line %d: expected %d tokens, got %d (tokens: %v)",
-				i, len(exp), len(lines[i].Tokens), lines[i].Tokens)
-			continue
-		}
-		for j, tok := range exp {
-			if lines[i].Tokens[j] != tok {
-				t.Errorf("line %d token %d: expected %q, got %q", i, j, tok, lines[i].Tokens[j])
-			}
-		}
-	}
-}
-
 func TestPreProcess_PragmaTracking(t *testing.T) {
 	files := map[string][]string{
 		"test.c65": {
@@ -657,8 +791,8 @@ func TestPreProcess_Halt(t *testing.T) {
 			"LINE1",
 			"LINE2",
 			"#HALT",
-			"LINE3", // should not be emitted
-			"LINE4", // should not be emitted
+			"LINE3",
+			"LINE4",
 		},
 	}
 	reader := NewMockFileReader(files)
@@ -672,7 +806,6 @@ func TestPreProcess_Halt(t *testing.T) {
 		t.Fatalf("expected HaltError, got %T: %v", err, err)
 	}
 
-	// Lines before HALT should still be processed
 	if len(lines) != 2 {
 		t.Errorf("expected 2 lines before halt, got %d", len(lines))
 	}
@@ -691,12 +824,12 @@ func TestPreProcess_HaltInInclude(t *testing.T) {
 		"main.c65": {
 			"MAIN_LINE1",
 			"#INCLUDE lib.c65",
-			"MAIN_LINE2", // should not be reached
+			"MAIN_LINE2",
 		},
 		"lib.c65": {
 			"LIB_LINE1",
 			"#HALT",
-			"LIB_LINE2", // should not be emitted
+			"LIB_LINE2",
 		},
 	}
 	reader := NewMockFileReader(files)
@@ -710,7 +843,6 @@ func TestPreProcess_HaltInInclude(t *testing.T) {
 		t.Fatalf("expected HaltError, got %T: %v", err, err)
 	}
 
-	// Should have MAIN_LINE1 and LIB_LINE1
 	if len(lines) != 2 {
 		t.Fatalf("expected 2 lines before halt, got %d", len(lines))
 	}
@@ -723,3 +855,94 @@ func TestPreProcess_HaltInInclude(t *testing.T) {
 		t.Errorf("expected LIB_LINE1, got %q", lines[1].Text)
 	}
 }
+
+func TestPreProcess_MixedBlocksAndComments(t *testing.T) {
+	files := map[string][]string{
+		"test.c65": {
+			"#DEFINE X = 10",
+			"LDA #X // source comment",
+			"ASM",
+			"  lda #X // asm comment",
+			"ENDASM",
+			"SCRIPT",
+			"  y = X // script comment",
+			"ENDSCRIPT",
+			"STA $D020 // another source comment",
+		},
+	}
+	reader := NewMockFileReader(files)
+	lines, err := PreProcess("test.c65", reader)
+	if err != nil {
+		t.Fatalf("PreProcess failed: %v", err)
+	}
+
+	expected := []struct {
+		text string
+		kind LineKind
+	}{
+		{"LDA #10", Source},
+		{"  lda #X // asm comment", Assembler},
+		{"  y = X // script comment", Script},
+		{"STA $D020", Source},
+	}
+
+	if len(lines) != len(expected) {
+		t.Fatalf("expected %d lines, got %d", len(expected), len(lines))
+	}
+
+	for i, exp := range expected {
+		if lines[i].Text != exp.text {
+			t.Errorf("line %d: expected text %q, got %q", i, exp.text, lines[i].Text)
+		}
+		if lines[i].Kind != exp.kind {
+			t.Errorf("line %d: expected Kind=%v, got %v", i, exp.kind, lines[i].Kind)
+		}
+	}
+}
+
+func TestPreProcess_EmptyASMBlock(t *testing.T) {
+	files := map[string][]string{
+		"test.c65": {
+			"ASM",
+			"ENDASM",
+			"NOP",
+		},
+	}
+	reader := NewMockFileReader(files)
+	lines, err := PreProcess("test.c65", reader)
+	if err != nil {
+		t.Fatalf("PreProcess failed: %v", err)
+	}
+
+	// Empty block produces no lines, just NOP
+	if len(lines) != 1 {
+		t.Fatalf("expected 1 line, got %d", len(lines))
+	}
+
+	if lines[0].Text != "NOP" {
+		t.Errorf("expected 'NOP', got %q", lines[0].Text)
+	}
+}
+
+func TestPreProcess_EmptyScriptBlock(t *testing.T) {
+	files := map[string][]string{
+		"test.c65": {
+			"SCRIPT",
+			"ENDSCRIPT",
+			"NOP",
+		},
+	}
+	reader := NewMockFileReader(files)
+	lines, err := PreProcess("test.c65", reader)
+	if err != nil {
+		t.Fatalf("PreProcess failed: %v", err)
+	}
+
+	if len(lines) != 1 {
+		t.Fatalf("expected 1 line, got %d", len(lines))
+	}
+
+	if lines[0].Text != "NOP" {
+		t.Errorf("expected 'NOP', got %q", lines[0].Text)
+	}
+}