diff --git a/befunge/src/main/kotlin/befide/befunge/b93/Befunge93.kt b/befunge/src/main/kotlin/befide/befunge/b93/Befunge93.kt
deleted file mode 100644
index 045b94d..0000000
--- a/befunge/src/main/kotlin/befide/befunge/b93/Befunge93.kt
+++ /dev/null
@@ -1,52 +0,0 @@
-package befide.befunge.b93
-
-import befide.befunge.b93.state.*
-import befide.befunge.core.*
-import befide.befunge.core.util.readAll
-import java.io.PipedReader
-import java.io.PipedWriter
-import java.util.*
-
-
-class Interpreter93(stdinSrc: PipedWriter, stdoutDest: PipedReader)
-    : MutableInterpreter<Vec2, Data93, PointerMode>() {
-
-    override val ip = Pointer93()
-    override val funge = Funge93()
-    override val stack = Stack<Data93>()
-
-    override fun stackDefault() = Data93.ZERO
-
-    override val stdin: PipedReader = PipedReader(stdinSrc)
-    override val stdout: PipedWriter = PipedWriter(stdoutDest)
-
-    override val instructionSet = B93Instructions() + B93Extras()
-}
-
-fun main(args: Array<String>) {
-    val stdinSrc = PipedWriter()
-    val stdoutDest = PipedReader()
-
-    val int = Interpreter93(stdinSrc, stdoutDest)
-
-    int.funge.onChange += { (pos, from, to) ->
-        println("$pos from $from to $to")
-    }
-
-    int.onIpChange += { (_, to) ->
-        println("ip to ${to.pos}")
-    }
-
-    int.funge.src = """2>:3g" "-!v\  g30          <
- |!`"O":+1_:.:03p>03g+:"O"`|
- @               ^  p3\" ":<
-2 234567890123456789012345678901234567890123456789012345678901234567890123456789"""
-
-//    int.funge.src = """fedc;ba9876;54321>:#._@"""
-
-    while (int.ip.mode != PointerMode.Terminated) {
-        int.step()
-    }
-
-    print(stdoutDest.readAll())
-}
\ No newline at end of file
diff --git a/befunge/src/main/kotlin/befide/befunge/b93/Instructions.kt b/befunge/src/main/kotlin/befide/befunge/b93/Instructions93.kt
similarity index 86%
rename from befunge/src/main/kotlin/befide/befunge/b93/Instructions.kt
rename to befunge/src/main/kotlin/befide/befunge/b93/Instructions93.kt
index a5b1b11..ec8fffa 100644
--- a/befunge/src/main/kotlin/befide/befunge/b93/Instructions.kt
+++ b/befunge/src/main/kotlin/befide/befunge/b93/Instructions93.kt
@@ -45,23 +45,27 @@ class B93Instructions : InstructionSet<Vec2, Data93, PointerMode> {
                 '\\' -> pop(2).let { (b, a) -> push(b, a) }
                 '$' -> pop(1)
 
-                '.' -> pop(1).let { (n) -> stdout.write("${n.data} ") }
-                ',' -> pop(1).let { (ch) -> stdout.write(ch.data.toChar().toString()) }
+                '.' -> pop(1).let { (n) -> stdout?.write("${n.data} ") }
+                ',' -> pop(1).let { (ch) -> stdout?.write(ch.data.toChar().toString()) }
 
                 'p' -> pop(3).let { (y, x, n) -> funge[Vec2(x.data.toInt(), y.data.toInt())] = n }
                 'g' -> pop(2).let { (y, x) -> push(funge[Vec2(x.data.toInt(), y.data.toInt())]) }
 
-                '~' -> push(Data93(stdin.read().toLong()))
+                '~' -> push(Data93(stdin?.read()?.toLong() ?: 0L))
                 '&' -> {
                     val chars = generateSequence {
-                        stdin.read().takeIf { it.toChar().isDigit() }
+                        stdin?.read()?.toChar()?.takeIf { it.isDigit() }
                     }
-                    val long = chars.joinToString("").toLong()
+                    val long = chars.joinToString("") {
+                        it.toString()
+                    }.ifEmpty { "0" }.toLong()
                     push(Data93(long))
                 }
 
                 '@' -> mode = PointerMode.Terminated
 
+                ' ' -> do move() while (next.char == ' ')
+
                 else -> return false
             }
         }
diff --git a/befunge/src/main/kotlin/befide/befunge/b93/Interpreter93.kt b/befunge/src/main/kotlin/befide/befunge/b93/Interpreter93.kt
new file mode 100644
index 0000000..45ca9cd
--- /dev/null
+++ b/befunge/src/main/kotlin/befide/befunge/b93/Interpreter93.kt
@@ -0,0 +1,31 @@
+package befide.befunge.b93
+
+import befide.befunge.b93.state.*
+import befide.befunge.core.*
+import befide.befunge.core.util.readAll
+import com.sun.imageio.spi.OutputStreamImageOutputStreamSpi
+import java.io.*
+import java.util.*
+import kotlin.concurrent.thread
+import kotlin.concurrent.timer
+
+
+class Interpreter93(override var stdin: Reader? = null, override var stdout: Writer? = null)
+    : MutableInterpreter<Vec2, Data93, PointerMode>() {
+
+    override val ip = Pointer93()
+    override val funge = Funge93()
+    override val stack = Stack<Data93>()
+
+    override fun stackDefault() = Data93.ZERO
+
+    override val instructionSet = B93Instructions() + B93Extras()
+
+    override fun run(afterEach: () -> Unit) {
+        while (mode != PointerMode.Terminated) {
+            step()
+            afterEach()
+            stdout?.flush()
+        }
+    }
+}
diff --git a/befunge/src/main/kotlin/befide/befunge/b93/Main.kt b/befunge/src/main/kotlin/befide/befunge/b93/Main.kt
new file mode 100644
index 0000000..edf38f3
--- /dev/null
+++ b/befunge/src/main/kotlin/befide/befunge/b93/Main.kt
@@ -0,0 +1,67 @@
+package befide.befunge.b93
+
+import befide.befunge.core.util.readAll
+import java.io.PipedReader
+import java.io.PipedWriter
+import kotlin.concurrent.thread
+import kotlin.concurrent.timer
+
+
+fun runSync() {
+    val int = Interpreter93(System.`in`.reader(), System.out.writer())
+
+    // interactive calculator
+    int.funge.src = "\" :b ]%/*-+[ a\">:#,_&~~\$a3*0p& .@"
+
+    int.run {}
+
+    println()
+}
+
+fun runThreaded() {
+    val stdout = PipedReader()
+    val stdin = PipedWriter()
+
+    val int = Interpreter93(PipedReader(stdin), PipedWriter(stdout))
+
+    // incrementer
+    int.funge.src = ":.&+"
+
+    val input = timer("input", period = 50L) {
+        generateSequence {
+            System.`in`.read().takeUnless { it == -1 }
+        }.forEach(stdin::write)
+    }
+
+    val output = timer("output", period = 500L) {
+        print(stdout.readAll())
+    }
+
+    val stepper = thread {
+        int.run { Thread.sleep(50L) }
+    }
+
+    // input, output, and computation happen concurrently at this point.
+
+    stepper.join()
+
+    input.cancel()
+    output.cancel()
+
+    println(stdout.readAll())
+
+    int.stdout?.close()
+    stdout.close()
+    int.stdin?.close()
+    stdin.close()
+}
+
+fun main(args: Array<String>) {
+    println("synchronous:")
+    runSync()
+
+    println()
+
+    println("threaded:")
+    runThreaded()
+}
\ No newline at end of file
diff --git a/befunge/src/main/kotlin/befide/befunge/b93/state/Vec2.kt b/befunge/src/main/kotlin/befide/befunge/b93/state/Vec93.kt
similarity index 100%
rename from befunge/src/main/kotlin/befide/befunge/b93/state/Vec2.kt
rename to befunge/src/main/kotlin/befide/befunge/b93/state/Vec93.kt
diff --git a/befunge/src/main/kotlin/befide/befunge/core/Interpreter.kt b/befunge/src/main/kotlin/befide/befunge/core/Interpreter.kt
index a2f201e..49a06e5 100644
--- a/befunge/src/main/kotlin/befide/befunge/core/Interpreter.kt
+++ b/befunge/src/main/kotlin/befide/befunge/core/Interpreter.kt
@@ -8,6 +8,8 @@ import befide.befunge.core.state.Pointer
 import befide.befunge.core.util.Event
 import java.io.PipedReader
 import java.io.PipedWriter
+import java.io.Reader
+import java.io.Writer
 
 interface Interpreter<V, D : Data, M : Enum<M>> {
     val ip: Pointer<V, M>
@@ -20,14 +22,15 @@ interface Interpreter<V, D : Data, M : Enum<M>> {
     val delta: V get() = ip.delta
     val pos: V get() = ip.pos
     val instr: D get() = funge[ip.pos]
+    val next: D get() = funge[funge.next(pos, delta)]
 
     val onIpChange: Event<IpChange<V, M>>
     val onStackChange: Event<StackChange<D>>
 
-    val stdin: PipedReader
-    val stdout: PipedWriter
+    var stdin: Reader?
+    val stdout: Writer?
 
     fun step()
-    fun reset()
+    fun run(afterEach: () -> Unit)
 }
 
diff --git a/befunge/src/main/kotlin/befide/befunge/core/MutableInterpreter.kt b/befunge/src/main/kotlin/befide/befunge/core/MutableInterpreter.kt
index 335cc61..67d10a2 100644
--- a/befunge/src/main/kotlin/befide/befunge/core/MutableInterpreter.kt
+++ b/befunge/src/main/kotlin/befide/befunge/core/MutableInterpreter.kt
@@ -68,9 +68,4 @@ abstract class MutableInterpreter<V, D : Data, M : Enum<M>>
             notifyStack(StackOp.Push) { stack.push(datum) }
         }
     }
-
-    override fun reset() {
-        stdin.readAll()
-        stdout.flush()
-    }
 }
\ No newline at end of file
diff --git a/befunge/src/main/kotlin/befide/befunge/core/util/Misc.kt b/befunge/src/main/kotlin/befide/befunge/core/util/Misc.kt
index c3f147d..f0b8902 100644
--- a/befunge/src/main/kotlin/befide/befunge/core/util/Misc.kt
+++ b/befunge/src/main/kotlin/befide/befunge/core/util/Misc.kt
@@ -1,6 +1,7 @@
 package befide.befunge.core.util
 
 import java.io.PipedReader
+import java.io.Reader
 import java.util.*
 import kotlin.random.Random
 
@@ -19,10 +20,8 @@ infix fun Long.mod(o: Long): Long {
 
 fun <T> List<T>.chooseOne(): T = this[Random.nextInt(size)]
 
-fun PipedReader.readAll(): String = generateSequence {
-    if (ready()) read().toChar() else null
-}.joinToString("")
+fun <T> Boolean.orNull(block: () -> T): T? = if (this) block() else null
 
-inline fun <reified T> Stack<T>.pop(n: Int): List<T> {
-    return (0 until n).map { pop() }
-}
\ No newline at end of file
+fun Reader.readAll(): String = generateSequence {
+    ready().orNull { read().toChar() }
+}.joinToString("")