diff --git a/app/src/main/java/com/example/tiptime/MainActivity.kt b/app/src/main/java/com/example/tiptime/MainActivity.kt
index 1d607a4..f932db9 100644
--- a/app/src/main/java/com/example/tiptime/MainActivity.kt
+++ b/app/src/main/java/com/example/tiptime/MainActivity.kt
@@ -1,30 +1,251 @@
+package com.example.tiptime
+
+import android.os.Bundle
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.setContent
+import androidx.activity.enableEdgeToEdge
 import androidx.annotation.DrawableRes
 import androidx.annotation.StringRes
 import androidx.compose.foundation.Image
-import androidx.compose.foundation.layout.Column
-import androidx.compose.foundation.layout.Row
-import androidx.compose.foundation.layout.Spacer
-import androidx.compose.foundation.layout.fillMaxWidth
-import androidx.compose.foundation.layout.padding
-import androidx.compose.foundation.layout.size
-import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.text.KeyboardActions
 import androidx.compose.foundation.text.KeyboardOptions
-import androidx.compose.material3.MaterialTheme
-import androidx.compose.material3.OutlinedTextField
-import androidx.compose.material3.Text
-import androidx.compose.runtime.Composable
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.*
+import androidx.compose.runtime.*
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.platform.LocalSoftwareKeyboardController
 import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.res.stringResource
-import androidx.compose.ui.semantics.error
+import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.input.ImeAction
 import androidx.compose.ui.text.input.KeyboardType
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import com.example.tiptime.ui.theme.TipTimeTheme
 
-// --- Composable InputWithImage DIPERBARUI dengan Batas Karakter ---
+class MainActivity : ComponentActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        enableEdgeToEdge()
+        super.onCreate(savedInstanceState)
+        setContent {
+            TipTimeTheme {
+                Surface(
+                    modifier = Modifier.fillMaxSize(),
+                    color = MaterialTheme.colorScheme.surfaceContainerLowest
+                ) {
+                    NavigationController()
+                }
+            }
+        }
+    }
+}
+
+// Navigasi tidak berubah
+private sealed class Screen {
+    object Start : Screen()
+    object Main : Screen()
+}
+
+@Composable
+private fun NavigationController() {
+    var currentScreen by remember { mutableStateOf<Screen>(Screen.Start) }
+
+    when (currentScreen) {
+        is Screen.Start -> {
+            StartScreen(onNavigateToMain = { currentScreen = Screen.Main })
+        }
+        is Screen.Main -> {
+            BMICalculatorScreen()
+        }
+    }
+}
+
+
+// --- VERSI DENGAN TOMBOL HITUNG ---
+@Composable
+fun BMICalculatorScreen() {
+    // --- State untuk input pengguna ---
+    var heightInput by remember { mutableStateOf("") }
+    var weightInput by remember { mutableStateOf("") }
+    var useMetric by remember { mutableStateOf(true) }
+
+    // --- State untuk hasil perhitungan (dipisah) ---
+    var calculatedBmi by remember { mutableStateOf(0.0) }
+
+    // State untuk status error
+    var isHeightError by remember { mutableStateOf(false) }
+    var isWeightError by remember { mutableStateOf(false) }
+
+    // Batas Maksimal
+    val maxHeightCm = 250.0
+    val maxWeightKg = 300.0
+
+    // Keyboard controller untuk menyembunyikan keyboard setelah tombol ditekan
+    val keyboardController = LocalSoftwareKeyboardController.current
+
+    // --- FUNGSI BARU YANG DIPANGGIL SAAT TOMBOL DITEKAN ---
+    fun performCalculation() {
+        keyboardController?.hide() // Sembunyikan keyboard
+
+        val height = heightInput.toDoubleOrNull() ?: 0.0
+        val weight = weightInput.toDoubleOrNull() ?: 0.0
+
+        // Lakukan validasi saat tombol ditekan
+        isHeightError = height <= 0 || height > maxHeightCm
+        isWeightError = weight <= 0 || weight > maxWeightKg
+
+        // Hanya hitung dan perbarui state hasil jika tidak ada error
+        if (!isHeightError && !isWeightError) {
+            calculatedBmi = calculateBMI(height, weight, useMetric)
+        } else {
+            calculatedBmi = 0.0 // Reset hasil jika ada error
+        }
+    }
+
+    // Menggunakan state hasil (calculatedBmi) untuk tampilan kartu atas
+    val bmiCategory = bmiCategory(calculatedBmi)
+    val bmiCategoryColor = getBmiCategoryColor(bmiCategory)
+
+    Column(
+        modifier = Modifier
+            .fillMaxSize()
+            .verticalScroll(rememberScrollState())
+            .safeDrawingPadding()
+            .padding(16.dp),
+        horizontalAlignment = Alignment.CenterHorizontally
+    ) {
+        Text(
+            text = stringResource(R.string.bmi_calculator),
+            style = MaterialTheme.typography.headlineLarge,
+            fontWeight = FontWeight.Bold,
+            modifier = Modifier.padding(vertical = 16.dp)
+        )
+
+        // --- Kartu Hasil BMI ---
+        Card(
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(bottom = 16.dp),
+            elevation = CardDefaults.cardElevation(defaultElevation = 8.dp),
+            colors = CardDefaults.cardColors(containerColor = MaterialTheme.colorScheme.surfaceContainer)
+        ) {
+            Column(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(24.dp),
+                horizontalAlignment = Alignment.CenterHorizontally,
+                verticalArrangement = Arrangement.Center
+            ) {
+                Text(
+                    text = stringResource(id = R.string.your_bmi_is),
+                    style = MaterialTheme.typography.titleMedium,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant
+                )
+                Text(
+                    // Menampilkan dari state hasil 'calculatedBmi'
+                    text = "%.1f".format(calculatedBmi),
+                    fontSize = 52.sp,
+                    fontWeight = FontWeight.ExtraBold,
+                    color = bmiCategoryColor
+                )
+                Spacer(modifier = Modifier.height(8.dp))
+                Text(
+                    text = bmiCategory,
+                    fontSize = 20.sp,
+                    fontWeight = FontWeight.SemiBold,
+                    color = bmiCategoryColor
+                )
+                Spacer(modifier = Modifier.height(16.dp))
+                BmiIndicatorBar(category = bmiCategory)
+            }
+        }
+
+        // --- Bagian Input Data ---
+        Column(
+            modifier = Modifier.fillMaxWidth(),
+            horizontalAlignment = Alignment.Start,
+            verticalArrangement = Arrangement.spacedBy(16.dp) // Jarak antar kartu
+        ) {
+            Text(
+                text = "Pengaturan & Input",
+                style = MaterialTheme.typography.titleMedium,
+                modifier = Modifier.padding(start = 8.dp, bottom = 8.dp),
+                fontWeight = FontWeight.Bold
+            )
+
+            Card(modifier = Modifier.fillMaxWidth()) {
+                UnitSwitchRow(
+                    isMetric = useMetric,
+                    onUnitChanged = { useMetric = it },
+                    modifier = Modifier.padding(horizontal = 16.dp, vertical = 8.dp)
+                )
+            }
+
+            Card(modifier = Modifier.fillMaxWidth()) {
+                InputWithImage(
+                    imageRes = R.drawable.ic_height,
+                    label = if (useMetric) R.string.height_cm else R.string.height_in,
+                    value = heightInput,
+                    onValueChanged = {
+                        heightInput = it
+                        // Reset error saat pengguna mulai mengetik lagi
+                        isHeightError = false
+                    },
+                    isError = isHeightError,
+                    errorMessage = "Input tidak valid (1-${maxHeightCm.toInt()})",
+                    imeAction = ImeAction.Next,
+                    modifier = Modifier.padding(16.dp)
+                )
+            }
+
+            Card(modifier = Modifier.fillMaxWidth()) {
+                InputWithImage(
+                    imageRes = R.drawable.ic_weight,
+                    label = if (useMetric) R.string.weight_kg else R.string.weight_lbs,
+                    value = weightInput,
+                    onValueChanged = {
+                        weightInput = it
+                        // Reset error saat pengguna mulai mengetik lagi
+                        isWeightError = false
+                    },
+                    isError = isWeightError,
+                    errorMessage = "Input tidak valid (1-${maxWeightKg.toInt()})",
+                    imeAction = ImeAction.Done,
+                    // Tambahkan keyboardActions untuk memicu perhitungan saat "Done" ditekan
+                    keyboardActions = KeyboardActions(onDone = { performCalculation() }),
+                    modifier = Modifier.padding(16.dp)
+                )
+            }
+        }
+
+        Spacer(modifier = Modifier.weight(1f)) // Spacer untuk mendorong tombol ke bawah
+
+        // --- TOMBOL HITUNG BARU ---
+        Button(
+            onClick = { performCalculation() }, // Panggil fungsi perhitungan
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(vertical = 16.dp)
+                .height(50.dp)
+        ) {
+            Text("HITUNG BMI", fontSize = 18.sp, fontWeight = FontWeight.Bold)
+        }
+    }
+}
+
+// --- Composable InputWithImage diperbarui ---
 @Composable
 fun InputWithImage(
     @DrawableRes imageRes: Int,
@@ -34,8 +255,7 @@ fun InputWithImage(
     isError: Boolean,
     errorMessage: String,
     imeAction: ImeAction,
-    maxLength: Int, // Parameter baru untuk batas maksimal karakter
-    keyboardActions: KeyboardActions = KeyboardActions.Default,
+    keyboardActions: KeyboardActions = KeyboardActions.Default, // Tambah parameter ini
     modifier: Modifier = Modifier
 ) {
     Row(
@@ -53,12 +273,7 @@ fun InputWithImage(
         Column(modifier = Modifier.weight(1f)) {
             OutlinedTextField(
                 value = value,
-                onValueChange = {
-                    // LOGIKA BARU UNTUK MEMBATASI INPUT
-                    if (it.length <= maxLength) {
-                        onValueChanged(it)
-                    }
-                },
+                onValueChange = onValueChanged,
                 label = { Text(stringResource(label)) },
                 keyboardOptions = KeyboardOptions(
                     keyboardType = KeyboardType.Number,
@@ -67,7 +282,7 @@ fun InputWithImage(
                 singleLine = true,
                 modifier = Modifier.fillMaxWidth(),
                 isError = isError,
-                keyboardActions = keyboardActions
+                keyboardActions = keyboardActions // Terapkan keyboardActions
             )
             if (isError) {
                 Text(
@@ -80,3 +295,96 @@ fun InputWithImage(
         }
     }
 }
+
+
+// --- FUNGSI-FUNGSI PEMBANTU LAINNYA ---
+// (Tidak ada perubahan signifikan di sini)
+
+@Composable
+fun BmiIndicatorBar(category: String) {
+    val categories = listOf("Underweight", "Normal", "Overweight", "Obese")
+    Row(
+        modifier = Modifier
+            .fillMaxWidth()
+            .height(16.dp)
+            .clip(CircleShape)
+            .background(MaterialTheme.colorScheme.surface)
+            .padding(2.dp)
+    ) {
+        categories.forEach { cat ->
+            Box(
+                modifier = Modifier
+                    .weight(1f)
+                    .fillMaxHeight()
+                    .background(
+                        if (cat == category) getBmiCategoryColor(cat) else Color.LightGray.copy(
+                            alpha = 0.3f
+                        )
+                    )
+            )
+        }
+    }
+}
+
+@Composable
+fun UnitSwitchRow(isMetric: Boolean, onUnitChanged: (Boolean) -> Unit, modifier: Modifier = Modifier) {
+    Row(
+        modifier = modifier.fillMaxWidth(),
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.SpaceBetween
+    ) {
+        Text("Unit", fontWeight = FontWeight.SemiBold)
+        Row(verticalAlignment = Alignment.CenterVertically) {
+            Text("Imperial", style = MaterialTheme.typography.bodyMedium)
+            Switch(
+                checked = isMetric,
+                onCheckedChange = onUnitChanged,
+                modifier = Modifier.padding(horizontal = 8.dp)
+            )
+            Text("Metric", style = MaterialTheme.typography.bodyMedium)
+        }
+    }
+}
+
+private fun calculateBMI(height: Double, weight: Double, isMetric: Boolean): Double {
+    if (height <= 0 || weight <= 0) return 0.0
+    if (height > 250 || weight > 300) return 0.0
+
+    return if (isMetric) {
+        val heightInMeters = height / 100
+        weight / (heightInMeters * heightInMeters)
+    } else {
+        703 * weight / (height * height)
+    }
+}
+
+private fun bmiCategory(bmi: Double): String {
+    return when {
+        bmi == 0.0 -> "..."
+        bmi < 18.5 -> "Underweight"
+        bmi < 25.0 -> "Normal"
+        bmi < 30.0 -> "Overweight"
+        else -> "Obese"
+    }
+}
+
+@Composable
+private fun getBmiCategoryColor(category: String): Color {
+    return when (category) {
+        "Underweight" -> Color(0xFF8AB4F8)
+        "Normal" -> Color(0xFF5BB974)
+        "Overweight" -> Color(0xFFFDD663)
+        "Obese" -> Color(0xFFE57373)
+        else -> MaterialTheme.colorScheme.onSurface
+    }
+}
+
+@Preview(showBackground = true, name = "Final BMI Calculator with Button")
+@Composable
+fun BMICalculatorScreenPreview() {
+    TipTimeTheme {
+        Surface(color = MaterialTheme.colorScheme.surfaceContainerLowest) {
+            BMICalculatorScreen()
+        }
+    }
+}