diff --git a/.idea/deploymentTargetSelector.xml b/.idea/deploymentTargetSelector.xml
index 2bd0f7d..64b9ca1 100644
--- a/.idea/deploymentTargetSelector.xml
+++ b/.idea/deploymentTargetSelector.xml
@@ -4,7 +4,7 @@
     <selectionStates>
       <SelectionState runConfigName="app">
         <option name="selectionMode" value="DROPDOWN" />
-        <DropdownSelection timestamp="2026-08-19T22:25:01.327233679Z">
+        <DropdownSelection timestamp="2026-08-20T13:53:52.273519182Z">
           <Target type="DEFAULT_BOOT">
             <handle>
               <DeviceId pluginId="LocalEmulator" identifier="path=/home/jasonross/.android/avd/Test_Device.avd" />
diff --git a/app/src/main/java/dev/jasonmross/mediaconverter/convert/ConverterScreen.kt b/app/src/main/java/dev/jasonmross/mediaconverter/convert/ConverterScreen.kt
index f0244f9..727d3fd 100644
--- a/app/src/main/java/dev/jasonmross/mediaconverter/convert/ConverterScreen.kt
+++ b/app/src/main/java/dev/jasonmross/mediaconverter/convert/ConverterScreen.kt
@@ -26,8 +26,10 @@ import androidx.compose.runtime.getValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.text.style.TextAlign
-import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
+import dev.jasonmross.mediaconverter.ui.PrimaryButtonHeight
+import dev.jasonmross.mediaconverter.ui.ScreenPaddingHorizontal
+import dev.jasonmross.mediaconverter.ui.ScreenPaddingVertical
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.lifecycle.viewmodel.compose.viewModel
 import androidx.media3.common.util.UnstableApi
@@ -36,17 +38,6 @@ import dev.jasonmross.mediaconverter.model.OutputFormat
 import dev.jasonmross.mediaconverter.model.QualityTier
 import java.util.Locale
 
-/** Primary actions are taller than the Material default so they read as the main affordance. */
-private val PrimaryButtonHeight: Dp = 56.dp
-
-/**
- * Horizontal screen inset.
- *
- * Deliberately tighter than the vertical inset so a full-width primary button reaches
- * close to both edges of the display.
- */
-private val ScreenPadding: Dp = 16.dp
-
 @UnstableApi
 @Composable
 fun ConverterScreen(
@@ -78,7 +69,7 @@ fun ConverterScreen(
     Column(
         modifier = modifier
             .fillMaxSize()
-            .padding(horizontal = ScreenPadding, vertical = 24.dp),
+            .padding(horizontal = ScreenPaddingHorizontal, vertical = ScreenPaddingVertical),
     ) {
         Text(
             "Media Converter",
diff --git a/app/src/main/java/dev/jasonmross/mediaconverter/join/JoinScreen.kt b/app/src/main/java/dev/jasonmross/mediaconverter/join/JoinScreen.kt
index 18471e6..0d40b3e 100644
--- a/app/src/main/java/dev/jasonmross/mediaconverter/join/JoinScreen.kt
+++ b/app/src/main/java/dev/jasonmross/mediaconverter/join/JoinScreen.kt
@@ -6,6 +6,7 @@ import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.verticalScroll
@@ -17,13 +18,18 @@ import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.unit.dp
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.lifecycle.viewmodel.compose.viewModel
 import androidx.media3.common.util.UnstableApi
 import dev.jasonmross.mediaconverter.convert.InputFile
 import dev.jasonmross.mediaconverter.model.ConcatStrategy
+import dev.jasonmross.mediaconverter.ui.PrimaryButtonHeight
+import dev.jasonmross.mediaconverter.ui.ScreenPaddingHorizontal
+import dev.jasonmross.mediaconverter.ui.ScreenPaddingVertical
 
 @UnstableApi
 @Composable
@@ -44,77 +50,125 @@ fun JoinScreen(
     Column(
         modifier = modifier
             .fillMaxSize()
-            .verticalScroll(rememberScrollState())
-            .padding(24.dp),
-        verticalArrangement = Arrangement.spacedBy(16.dp),
+            .padding(horizontal = ScreenPaddingHorizontal, vertical = ScreenPaddingVertical),
     ) {
-        Text("Join files", style = MaterialTheme.typography.headlineMedium)
+        Text(
+            "Join files",
+            style = MaterialTheme.typography.headlineMedium,
+            modifier = Modifier.padding(bottom = 16.dp),
+        )
+
+        // Same split as the converter screen: the empty state is centred, the working
+        // states scroll because their content can exceed the screen.
+        val body = Modifier.fillMaxWidth().weight(1f)
 
         when (val s = state) {
-            is JoinState.Idle -> {
+            is JoinState.Idle -> Column(
+                modifier = body,
+                verticalArrangement = Arrangement.Center,
+                horizontalAlignment = Alignment.CenterHorizontally,
+            ) {
                 Text(
                     "Pick two or more files to join, in the order you want them.",
                     style = MaterialTheme.typography.bodyMedium,
+                    textAlign = TextAlign.Center,
+                    modifier = Modifier.padding(bottom = 16.dp),
                 )
-                Button(onClick = { pickInputs.launch(arrayOf("video/*")) }) {
-                    Text("Choose files")
+                Button(
+                    onClick = { pickInputs.launch(arrayOf("video/*")) },
+                    modifier = Modifier
+                        .fillMaxWidth()
+                        .height(PrimaryButtonHeight),
+                ) { Text("Choose files") }
+            }
+
+            else -> Column(
+                modifier = body.verticalScroll(rememberScrollState()),
+                verticalArrangement = Arrangement.spacedBy(16.dp),
+            ) {
+                when (s) {
+                    is JoinState.Idle -> Unit
+
+                    is JoinState.Ready -> {
+                        s.inputs.forEach { FileRow(it) }
+                        Button(
+                            onClick = viewModel::join,
+                            modifier = Modifier.fillMaxWidth().height(PrimaryButtonHeight),
+                        ) { Text("Join ${s.inputs.size} files") }
+                        OutlinedButton(
+                            onClick = { pickInputs.launch(arrayOf("video/*")) },
+                            modifier = Modifier.fillMaxWidth(),
+                        ) { Text("Choose different files") }
+                    }
+
+                    is JoinState.Joining -> {
+                        Text("Joining ${s.inputs.size} files…")
+                        // Indeterminate on purpose: FFmpeg reports progress against a
+                        // single input's duration, which means nothing across a
+                        // concatenation. A fabricated percentage would be worse than none.
+                        LinearProgressIndicator(modifier = Modifier.fillMaxWidth())
+                        OutlinedButton(
+                            onClick = viewModel::cancel,
+                            modifier = Modifier.fillMaxWidth(),
+                        ) { Text("Cancel") }
+                    }
+
+                    is JoinState.Waiting -> {
+                        Text(
+                            "Paused. The system limits background media processing to " +
+                                "six hours a day, so this will resume automatically.",
+                            style = MaterialTheme.typography.bodyMedium,
+                        )
+                        OutlinedButton(
+                            onClick = viewModel::cancel,
+                            modifier = Modifier.fillMaxWidth(),
+                        ) { Text("Cancel") }
+                    }
+
+                    is JoinState.Joined -> {
+                        Text("Joined — ${s.staged.length() / 1_000_000} MB.")
+                        Text(
+                            when (s.strategy) {
+                                ConcatStrategy.STREAM_COPY ->
+                                    "Files matched, so they were joined without " +
+                                        "re-encoding — no quality loss."
+                                ConcatStrategy.REENCODE ->
+                                    "Files differed in format, so they were re-encoded " +
+                                        "to match."
+                            },
+                            style = MaterialTheme.typography.bodySmall,
+                        )
+                        Button(
+                            onClick = { chooseDestination.launch("joined.mp4") },
+                            modifier = Modifier.fillMaxWidth().height(PrimaryButtonHeight),
+                        ) { Text("Save file") }
+                        OutlinedButton(
+                            onClick = viewModel::reset,
+                            modifier = Modifier.fillMaxWidth(),
+                        ) { Text("Start over") }
+                    }
+
+                    is JoinState.Saved -> {
+                        Text("Saved ${s.displayName}.", style = MaterialTheme.typography.bodyLarge)
+                        Button(
+                            onClick = viewModel::reset,
+                            modifier = Modifier.fillMaxWidth().height(PrimaryButtonHeight),
+                        ) { Text("Join more") }
+                    }
+
+                    is JoinState.Failed -> {
+                        Text(
+                            s.message,
+                            color = MaterialTheme.colorScheme.error,
+                            style = MaterialTheme.typography.bodyMedium,
+                        )
+                        Button(
+                            onClick = viewModel::reset,
+                            modifier = Modifier.fillMaxWidth().height(PrimaryButtonHeight),
+                        ) { Text("Start over") }
+                    }
                 }
             }
-
-            is JoinState.Ready -> {
-                s.inputs.forEach { FileRow(it) }
-                Button(onClick = viewModel::join) { Text("Join ${s.inputs.size} files") }
-                OutlinedButton(onClick = { pickInputs.launch(arrayOf("video/*")) }) {
-                    Text("Choose different files")
-                }
-            }
-
-            is JoinState.Joining -> {
-                Text("Joining ${s.inputs.size} files…")
-                // Indeterminate on purpose: FFmpeg reports progress against a single
-                // input's duration, which means nothing across a concatenation. A
-                // fabricated percentage would be worse than none.
-                LinearProgressIndicator(modifier = Modifier.fillMaxWidth())
-                OutlinedButton(onClick = viewModel::cancel) { Text("Cancel") }
-            }
-
-            is JoinState.Waiting -> {
-                Text(
-                    "Paused. The system limits background media processing to six " +
-                        "hours a day, so this will resume automatically.",
-                    style = MaterialTheme.typography.bodyMedium,
-                )
-                OutlinedButton(onClick = viewModel::cancel) { Text("Cancel") }
-            }
-
-            is JoinState.Joined -> {
-                Text("Joined — ${s.staged.length() / 1_000_000} MB.")
-                Text(
-                    when (s.strategy) {
-                        ConcatStrategy.STREAM_COPY ->
-                            "Files matched, so they were joined without re-encoding — no quality loss."
-                        ConcatStrategy.REENCODE ->
-                            "Files differed in format, so they were re-encoded to match."
-                    },
-                    style = MaterialTheme.typography.bodySmall,
-                )
-                Button(onClick = { chooseDestination.launch("joined.mp4") }) { Text("Save file") }
-                OutlinedButton(onClick = viewModel::reset) { Text("Start over") }
-            }
-
-            is JoinState.Saved -> {
-                Text("Saved ${s.displayName}.", style = MaterialTheme.typography.bodyLarge)
-                Button(onClick = viewModel::reset) { Text("Join more") }
-            }
-
-            is JoinState.Failed -> {
-                Text(
-                    s.message,
-                    color = MaterialTheme.colorScheme.error,
-                    style = MaterialTheme.typography.bodyMedium,
-                )
-                Button(onClick = viewModel::reset) { Text("Start over") }
-            }
         }
     }
 }
diff --git a/app/src/main/java/dev/jasonmross/mediaconverter/ui/Dimens.kt b/app/src/main/java/dev/jasonmross/mediaconverter/ui/Dimens.kt
new file mode 100644
index 0000000..4d6811d
--- /dev/null
+++ b/app/src/main/java/dev/jasonmross/mediaconverter/ui/Dimens.kt
@@ -0,0 +1,24 @@
+package dev.jasonmross.mediaconverter.ui
+
+import androidx.compose.ui.unit.Dp
+import androidx.compose.ui.unit.dp
+
+/**
+ * Layout constants shared by the top-level screens.
+ *
+ * Shared rather than duplicated so the two tabs cannot drift apart: an empty state that
+ * looks different depending on which tab you are on reads as a bug.
+ */
+
+/** Primary actions are taller than the Material default so they read as the main affordance. */
+val PrimaryButtonHeight: Dp = 56.dp
+
+/**
+ * Horizontal screen inset.
+ *
+ * Deliberately tighter than the vertical inset so a full-width primary button reaches
+ * close to both edges of the display.
+ */
+val ScreenPaddingHorizontal: Dp = 16.dp
+
+val ScreenPaddingVertical: Dp = 24.dp