diff --git a/app/build.gradle.kts b/app/build.gradle.kts
index fea8cbb..5bd99bf 100644
--- a/app/build.gradle.kts
+++ b/app/build.gradle.kts
@@ -53,7 +53,10 @@ dependencies {
     implementation(libs.androidx.compose.ui)
     implementation(libs.androidx.compose.ui.tooling.preview)
     implementation(libs.androidx.compose.material3)
+    implementation(libs.kotlinx.collections.immutable)
 
     debugImplementation(platform(libs.androidx.compose.bom))
     debugImplementation(libs.androidx.compose.ui.tooling)
+
+    lintChecks(libs.compose.lint.checks)
 }
diff --git a/app/src/main/kotlin/com/juandiana/reflexgame/ui/MainScreen.kt b/app/src/main/kotlin/com/juandiana/reflexgame/ui/MainScreen.kt
index 02d8063..d85dcaa 100644
--- a/app/src/main/kotlin/com/juandiana/reflexgame/ui/MainScreen.kt
+++ b/app/src/main/kotlin/com/juandiana/reflexgame/ui/MainScreen.kt
@@ -29,8 +29,10 @@ import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.juandiana.reflexgame.R
+import com.juandiana.reflexgame.ui.theme.ExtendedReflexGameTheme
 import com.juandiana.reflexgame.ui.theme.ReflexGameTheme
-import com.juandiana.reflexgame.ui.theme.spacing
+import kotlinx.collections.immutable.ImmutableList
+import kotlinx.collections.immutable.persistentListOf
 import java.util.Locale
 
 @Composable
@@ -51,19 +53,20 @@ fun MainScreenRoute(viewModel: MainViewModel) {
 @Composable
 fun MainScreen(
     showTitle: Boolean,
-    squares: List<SquareState>,
+    squares: ImmutableList<SquareState>,
     scoreText: String,
     buttonText: String,
     elapsedTimeText: String,
     columnCount: Int,
     onSquareTouched: (Int) -> Unit,
-    onButtonClicked: () -> Unit
+    onButtonClicked: () -> Unit,
+    modifier: Modifier = Modifier
 ) {
-    Surface(modifier = Modifier.fillMaxSize()) {
+    Surface(modifier = modifier.fillMaxSize()) {
         Column(
             modifier = Modifier
                 .fillMaxSize()
-                .padding(MaterialTheme.spacing.medium)
+                .padding(ExtendedReflexGameTheme.spacing.medium)
         ) {
             Text(
                 modifier = Modifier
@@ -72,20 +75,20 @@ fun MainScreen(
                 text = stringResource(id = R.string.game_over).uppercase(Locale.getDefault()),
                 style = MaterialTheme.typography.displayLarge
             )
-            Spacer(modifier = Modifier.height(MaterialTheme.spacing.medium))
+            Spacer(modifier = Modifier.height(ExtendedReflexGameTheme.spacing.medium))
             SquaresGrid(
                 modifier = Modifier.fillMaxWidth(),
                 squares = squares,
                 columnCount = columnCount,
                 onSquareTouched = onSquareTouched
             )
-            Spacer(modifier = Modifier.height(MaterialTheme.spacing.medium))
+            Spacer(modifier = Modifier.height(ExtendedReflexGameTheme.spacing.medium))
             HeadsUpDisplay(
                 modifier = Modifier.fillMaxWidth(),
                 scoreText = scoreText,
                 elapsedTimeText = elapsedTimeText
             )
-            Spacer(modifier = Modifier.height(MaterialTheme.spacing.medium))
+            Spacer(modifier = Modifier.height(ExtendedReflexGameTheme.spacing.medium))
             Button(
                 onClick = onButtonClicked,
                 modifier = Modifier.fillMaxWidth()
@@ -101,7 +104,7 @@ fun MainScreen(
 
 @Composable
 private fun SquaresGrid(
-    squares: List<SquareState>,
+    squares: ImmutableList<SquareState>,
     columnCount: Int,
     onSquareTouched: (Int) -> Unit,
     modifier: Modifier = Modifier
@@ -109,7 +112,7 @@ private fun SquaresGrid(
     Column(
         modifier = modifier
             .background(Color.Black)
-            .padding(MaterialTheme.spacing.border)
+            .padding(ExtendedReflexGameTheme.spacing.border)
     ) {
         squares.chunked(columnCount).forEachIndexed { rowIndex, rowSquares ->
             Row(modifier = Modifier.fillMaxWidth()) {
@@ -137,7 +140,7 @@ private fun SquaresGrid(
 private fun HeadsUpDisplay(
     scoreText: String,
     elapsedTimeText: String,
-    modifier: Modifier
+    modifier: Modifier = Modifier
 ) {
     Row(
         modifier = modifier,
@@ -147,7 +150,7 @@ private fun HeadsUpDisplay(
             text = stringResource(id = R.string.score),
             fontWeight = FontWeight.Bold
         )
-        Spacer(modifier = Modifier.width(MaterialTheme.spacing.small))
+        Spacer(modifier = Modifier.width(ExtendedReflexGameTheme.spacing.small))
         Text(
             modifier = Modifier.weight(1f),
             text = scoreText
@@ -156,7 +159,7 @@ private fun HeadsUpDisplay(
             text = stringResource(id = R.string.time),
             fontWeight = FontWeight.Bold
         )
-        Spacer(modifier = Modifier.width(MaterialTheme.spacing.small))
+        Spacer(modifier = Modifier.width(ExtendedReflexGameTheme.spacing.small))
         Text(text = elapsedTimeText)
     }
 }
@@ -167,7 +170,7 @@ private fun SquareItem(
     onSquareTouched: () -> Unit,
     modifier: Modifier = Modifier
 ) {
-    val border = MaterialTheme.spacing.border
+    val border = ExtendedReflexGameTheme.spacing.border
     val color = when (squareState) {
         SquareState.CLEAR -> Color.White
         SquareState.FLASHED -> Color.Blue
@@ -198,7 +201,7 @@ private fun MainScreenPreview() {
     ReflexGameTheme {
         MainScreen(
             showTitle = false,
-            squares = listOf(
+            squares = persistentListOf(
                 SquareState.CLEAR,
                 SquareState.FLASHED,
                 SquareState.CLEAR,
diff --git a/app/src/main/kotlin/com/juandiana/reflexgame/ui/MainScreenState.kt b/app/src/main/kotlin/com/juandiana/reflexgame/ui/MainScreenState.kt
index 5c41098..dc5178b 100644
--- a/app/src/main/kotlin/com/juandiana/reflexgame/ui/MainScreenState.kt
+++ b/app/src/main/kotlin/com/juandiana/reflexgame/ui/MainScreenState.kt
@@ -1,5 +1,7 @@
 package com.juandiana.reflexgame.ui
 
+import kotlinx.collections.immutable.ImmutableList
+
 enum class SquareState {
     CLEAR,
     FLASHED,
@@ -9,7 +11,7 @@ enum class SquareState {
 
 data class MainScreenState(
     val showTitle: Boolean,
-    val squares: List<SquareState>,
+    val squares: ImmutableList<SquareState>,
     val scoreText: String,
     val buttonText: String,
     val elapsedTimeText: String
diff --git a/app/src/main/kotlin/com/juandiana/reflexgame/ui/MainViewModel.kt b/app/src/main/kotlin/com/juandiana/reflexgame/ui/MainViewModel.kt
index 4a91c56..7a82ddb 100644
--- a/app/src/main/kotlin/com/juandiana/reflexgame/ui/MainViewModel.kt
+++ b/app/src/main/kotlin/com/juandiana/reflexgame/ui/MainViewModel.kt
@@ -14,6 +14,8 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
+import kotlinx.collections.immutable.ImmutableList
+import kotlinx.collections.immutable.toImmutableList
 
 class MainViewModel(
     private val resourcesProvider: ResourcesProvider,
@@ -99,7 +101,7 @@ class MainViewModel(
                     } else {
                         SquareState.CLEAR
                     }
-                }
+                }.toImmutableList()
             )
         }
 
@@ -117,7 +119,7 @@ class MainViewModel(
                     } else {
                         SquareState.CLEAR
                     }
-                }
+                }.toImmutableList()
             )
         }
 
@@ -135,7 +137,8 @@ class MainViewModel(
         }
     }
 
-    private fun clearSquares(): List<SquareState> = List(gameEngine.squaresCount) { SquareState.CLEAR }
+    private fun clearSquares(): ImmutableList<SquareState> =
+        List(gameEngine.squaresCount) { SquareState.CLEAR }.toImmutableList()
 
     private fun elapsedSecondsSince(startTime: Long): Long {
         return ((SystemClock.elapsedRealtime() - startTime) / 1000L).coerceAtLeast(0L)
diff --git a/app/src/main/kotlin/com/juandiana/reflexgame/ui/theme/Spacing.kt b/app/src/main/kotlin/com/juandiana/reflexgame/ui/theme/Spacing.kt
index 9136913..6195e8e 100644
--- a/app/src/main/kotlin/com/juandiana/reflexgame/ui/theme/Spacing.kt
+++ b/app/src/main/kotlin/com/juandiana/reflexgame/ui/theme/Spacing.kt
@@ -1,7 +1,6 @@
 package com.juandiana.reflexgame.ui.theme
 
-import androidx.compose.material3.MaterialTheme
-import androidx.compose.runtime.Composable
+import android.annotation.SuppressLint
 import androidx.compose.runtime.Immutable
 import androidx.compose.runtime.staticCompositionLocalOf
 import androidx.compose.ui.unit.Dp
@@ -14,8 +13,5 @@ internal data class ReflexGameSpacing(
     val medium: Dp = 16.dp
 )
 
+@SuppressLint("ComposeCompositionLocalUsage")
 internal val LocalReflexGameSpacing = staticCompositionLocalOf { ReflexGameSpacing() }
-
-internal val MaterialTheme.spacing: ReflexGameSpacing
-    @Composable
-    get() = LocalReflexGameSpacing.current
diff --git a/app/src/main/kotlin/com/juandiana/reflexgame/ui/theme/Theme.kt b/app/src/main/kotlin/com/juandiana/reflexgame/ui/theme/Theme.kt
index c505e88..d72b710 100644
--- a/app/src/main/kotlin/com/juandiana/reflexgame/ui/theme/Theme.kt
+++ b/app/src/main/kotlin/com/juandiana/reflexgame/ui/theme/Theme.kt
@@ -12,15 +12,18 @@ private val ReflexGameLightColorScheme = lightColorScheme(
     onSecondary = Black
 )
 
+internal object ExtendedReflexGameTheme {
+    val spacing: ReflexGameSpacing
+        @Composable
+        get() = LocalReflexGameSpacing.current
+}
+
 @Composable
 internal fun ReflexGameTheme(content: @Composable () -> Unit) {
-    MaterialTheme(
-        colorScheme = ReflexGameLightColorScheme,
-        typography = ReflexGameTypography
-    ) {
-        CompositionLocalProvider(
-            LocalReflexGameSpacing provides ReflexGameSpacing(),
-            content = content
-        )
+    CompositionLocalProvider(LocalReflexGameSpacing provides ReflexGameSpacing()) {
+        MaterialTheme(
+            colorScheme = ReflexGameLightColorScheme,
+            typography = ReflexGameTypography
+        ) { content() }
     }
 }
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index bd7bc67..3a876a7 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -1,15 +1,18 @@
 [versions]
 android-gradle-plugin = "9.0.1"
 kotlin = "2.3.10"
+kotlinx-collections-immutable = "0.4.0"
 androidx-activity = "1.12.4"
 androidx-lifecycle = "2.10.0"
 androidx-compose-bom = "2026.02.00"
+compose-lints = "1.4.2"
 
 [plugins]
 android-application = { id = "com.android.application", version.ref = "android-gradle-plugin" }
 kotlin-compose = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "kotlin" }
 
 [libraries]
+kotlinx-collections-immutable = { module = "org.jetbrains.kotlinx:kotlinx-collections-immutable", version.ref = "kotlinx-collections-immutable" }
 androidx-activity-compose = { module = "androidx.activity:activity-compose", version.ref = "androidx-activity" }
 androidx-lifecycle-viewmodel-ktx = { module = "androidx.lifecycle:lifecycle-viewmodel-ktx", version.ref = "androidx-lifecycle" }
 androidx-lifecycle-runtime-compose = { module = "androidx.lifecycle:lifecycle-runtime-compose", version.ref = "androidx-lifecycle" }
@@ -18,3 +21,4 @@ androidx-compose-ui = { module = "androidx.compose.ui:ui" }
 androidx-compose-ui-tooling = { module = "androidx.compose.ui:ui-tooling" }
 androidx-compose-ui-tooling-preview = { module = "androidx.compose.ui:ui-tooling-preview" }
 androidx-compose-material3 = { module = "androidx.compose.material3:material3" }
+compose-lint-checks = { module = "com.slack.lint.compose:compose-lint-checks", version.ref = "compose-lints" }