diff --git a/day22/block.go b/day22/block.go
index dd8b1db..165f4ac 100644
--- a/day22/block.go
+++ b/day22/block.go
@@ -7,6 +7,7 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"github.com/deckarep/golang-set/v2"
 )
 
 type XY struct {
@@ -20,8 +21,8 @@ type Block struct {
 	Z           uint
 	IsSettled   bool
 	ZHeight     uint
-	Supports    []*Block
-	SupportedBy []*Block
+	Supports    mapset.Set[*Block]
+	SupportedBy mapset.Set[*Block]
 }
 
 func (b *Block) String() string {
@@ -53,6 +54,9 @@ func ReadBlock(line string, num int) (b Block) {
 	b.Z = uint(min(z1, z2))
 	b.ZHeight = uint(max(z1, z2)) - b.Z
 
+	b.Supports = mapset.NewSet[*Block]()
+	b.SupportedBy = mapset.NewSet[*Block]()
+
 	return
 }
 
diff --git a/day22/notes.org b/day22/notes.org
index 0fae979..35e9641 100644
--- a/day22/notes.org
+++ b/day22/notes.org
@@ -72,3 +72,5 @@ slices.SortFunc(block.SupportedBy, func(a *Block, b *Block) int {
 })
 block.SupportedBy = slices.Compact(block.SupportedBy)
 #+end_src
+* maybe rewrite with Set?
+* should have done that from the start
diff --git a/day22/sandSlabs.go b/day22/sandSlabs.go
index 2476633..9daf944 100644
--- a/day22/sandSlabs.go
+++ b/day22/sandSlabs.go
@@ -6,7 +6,7 @@ import (
 
 func Run() int {
 	fmt.Print("oi, hello day 22")
-	filename := "day22/example"
+	filename := "day22/input"
 	blocks := ReadBlockFile(filename)
 	byZ := BlocksByZ(blocks)
 
diff --git a/day22/space.go b/day22/space.go
index c443790..6e8ce53 100644
--- a/day22/space.go
+++ b/day22/space.go
@@ -1,11 +1,8 @@
 package day22
 
 import (
-	// "fmt"
-	"cmp"
 	"log"
 	"slices"
-	// "time"
 )
 
 type Space struct {
@@ -29,8 +26,8 @@ func (s *Space) AgainCountFreeBlocks() (result int) {
 		for _, block := range row {
 			thisSupports := block.Supports
 			canDisintegrate := true
-			for _, blockThisSupports := range thisSupports {
-				if len(blockThisSupports.SupportedBy) == 1 {
+			for blockThisSupports := range thisSupports.Iter() {
+				if blockThisSupports.SupportedBy.Cardinality() == 1 {
 					// we cannot disintigrate this block
 					canDisintegrate = false
 				}
@@ -49,8 +46,8 @@ func (s *Space) InitialCollectGoodToDisintegrate() (result []Block) {
 	for _, row := range s.SettledOnZ {
 		for _, block := range row {
 			allBlocks[block] = struct{}{}
-			if len(block.SupportedBy) == 1 {
-				onlySupport := block.SupportedBy[0]
+			if block.SupportedBy.Cardinality() == 1 {
+				onlySupport, _ := block.SupportedBy.Pop()
 				log.Printf("in block %+v. only support is %+v", block, onlySupport)
 				log.Printf("should be NOT OK to remove %+v", onlySupport)
 				delete(allBlocks, onlySupport)
@@ -189,8 +186,9 @@ func (s *Space) SettleBlock(block *Block) (hasMoved bool) {
 	}
 
 	for _, settledUnderblock := range underZBlocks {
-		settledUnderblock.Supports = append(settledUnderblock.Supports, block)
-		block.SupportedBy = append(block.SupportedBy, settledUnderblock)
+		settledUnderblock.Supports.Add(block)
+		block.SupportedBy.Add(settledUnderblock)
+
 	}
 
 	block.Z = underZMax + 1
@@ -199,11 +197,6 @@ func (s *Space) SettleBlock(block *Block) (hasMoved bool) {
 	s.SettledOnZ[block.Z] = append(s.SettledOnZ[block.Z], block)
 	// fmt.Printf(">> after settring block %s. supported by %+v\n\n", block, block.SupportedBy)
 
-	slices.SortFunc(block.SupportedBy, func(a *Block, b *Block) int {
-		return cmp.Compare(a.NameNum, b.NameNum)
-	})
-	block.SupportedBy = slices.Compact(block.SupportedBy)
-
 	// time.Sleep(500 * time.Millisecond)
 	hasMoved = initialZ != block.Z
 	// if hasMoved {
diff --git a/go.mod b/go.mod
index 6c21a56..9f796c3 100644
--- a/go.mod
+++ b/go.mod
@@ -2,7 +2,10 @@ module sunshine.industries/aoc2023
 
 go 1.21.4
 
-require github.com/tidwall/pinhole v0.0.0-20210130162507-d8644a7c3d19
+require (
+	github.com/deckarep/golang-set/v2 v2.5.0
+	github.com/tidwall/pinhole v0.0.0-20210130162507-d8644a7c3d19
+)
 
 require (
 	github.com/fogleman/gg v1.3.0 // indirect
diff --git a/go.sum b/go.sum
index f788e65..660527a 100644
--- a/go.sum
+++ b/go.sum
@@ -1,3 +1,5 @@
+github.com/deckarep/golang-set/v2 v2.5.0 h1:hn6cEZtQ0h3J8kFrHR/NrzyOoTnjgW1+FmNJzQ7y/sA=
+github.com/deckarep/golang-set/v2 v2.5.0/go.mod h1:VAky9rY/yGXJOLEDv3OMci+7wtDpOF4IN+y82NBOac4=
 github.com/fogleman/gg v1.3.0 h1:/7zJX8F6AaYQc57WQCyN9cAIz+4bCJGO9B+dyW29am8=
 github.com/fogleman/gg v1.3.0/go.mod h1:R/bRT+9gY/C5z7JzPU0zXsXHKM4/ayA+zqcVNZzPa1k=
 github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF08vX0COfcOBJRhZ8lUbR+ZWIs0Y5g=