add backspace to zero field, fix input stack effects

main.usm

@@ -115,7 +115,8 @@ RTN
 	DUP #10 AND ,&up JCN ( check the if the four directions are pressed )
 	DUP #20 AND ,&down JCN
 	DUP #40 AND ,&left JCN
-	#80 AND ,&right JCN
+	DUP #80 AND ,&right JCN
+	POP
 	RTN ( if none are pressed, break )
 	&up
 	POP ( pop the controller )
@@ -123,8 +124,8 @@ RTN
 	.Edit/selection-y LDZ #01 SUB .Edit/selection-y STZ
 	RTN
 	&down
-	POP2
-	PTN_LEN #0001 SUB2 .Edit/selection-y LDZ EQU ,&end JCN
+	POP
+	PTN_LEN #0001 SUB2 LOB .Edit/selection-y LDZ EQU ,&end JCN
 	.Edit/selection-y LDZ #01 ADD .Edit/selection-y STZ
 	RTN
 	&left 
@@ -134,14 +135,16 @@ RTN
 	RTN
 	&right
 	POP
-	PTN_WIDTH #0001 SUB2 .Edit/selection-x LDZ EQU ,&end JCN
+	PTN_WIDTH #0001 SUB2 LOB .Edit/selection-x LDZ EQU ,&end JCN
 	.Edit/selection-x LDZ #01 ADD .Edit/selection-x STZ
 	&end
 RTN
 
 @handle-editing ( key -- )
 	DUP #2b EQU ,&plus JCN
-	#2d EQU ,&minus JCN
+	DUP #2d EQU ,&minus JCN
+	DUP #08 EQU ,&bksp JCN
+	POP
 	RTN
 	&plus
 	POP ( pop the key )
@@ -150,10 +153,15 @@ RTN
 	LDA #01 ADD STH2r STA
 	RTN
 	&minus
+	POP
 	#00 .Edit/selection-x LDZ EQU ;get-selected-addr JSR2 LDA #0c EQU AND ,&end JCN ( if we're on a note and out of bounds, skip moving )
 	;get-selected-addr JSR2 DUP2 STH2 ( stash selection address and keep another copy on the stack )
 	LDA #01 SUB STH2r STA
 	RTN
+	&bksp
+	POP
+	#00 ;get-selected-addr JSR2 STA
+	RTN
 	&end
 RTN
 
@@ -176,7 +184,6 @@ RTN
     BRK
   	&prev
   	POP
-
   	.Playback/pattern-index LDZ #01 SUB .Playback/pattern-index STZ
     .Playback/pattern-index LDZ ;alloc-load-pattern JSR2
   	BRK