diff --git a/package.json b/package.json
index 0d1563a..8fa5efe 100644
--- a/package.json
+++ b/package.json
@@ -24,6 +24,8 @@
   "dependencies": {
     "babel-runtime": "^5.4.4",
     "emit-then": "^1.0.2",
+    "event-promise": "0.0.1",
+    "flatmap": "0.0.3",
     "minecraft-data": "0.7.0",
     "minecraft-protocol": "0.16.3",
     "mkdirp": "0.5.1",
@@ -38,11 +40,11 @@
     "prismarine-world": "0.3.3",
     "prismarine-world-sync": "0.1.0",
     "random-seed": "^0.2.0",
+    "range": "0.0.3",
     "request-promise": "^0.4.3",
     "requireindex": "~1.0.0",
     "spiralloop": "1.0.2",
-    "vec3": "0.1.3",
-    "event-promise": "0.0.1"
+    "vec3": "0.1.3"
   },
   "license": "MIT",
   "repository": {
diff --git a/src/index.js b/src/index.js
index 87a4874..65e1a30 100644
--- a/src/index.js
+++ b/src/index.js
@@ -14,7 +14,8 @@ module.exports = {
   version:require("./lib/version"),
   generations:require("./lib/generations"),
   experience:require("./lib/experience"),
-  UserError:require("./lib/user_error")
+  UserError:require("./lib/user_error"),
+  portal_detector:require('./lib/portal_detector')
 };
 
 function createMCServer(options) {
diff --git a/src/lib/plugins/useItem.js b/src/lib/plugins/useItem.js
new file mode 100644
index 0000000..4eef4e1
--- /dev/null
+++ b/src/lib/plugins/useItem.js
@@ -0,0 +1,30 @@
+var items=require("minecraft-data")(require("flying-squid").version).items;
+var Vec3 = require("vec3").Vec3;
+var {detectFrame,getAir}=require("flying-squid").portal_detector;
+
+module.exports.player=function(player,serv)
+{
+  player._client.on("block_place",({direction,heldItem,location} = {}) => {
+    if (direction == -1 || heldItem.blockId == -1 || !items[heldItem.blockId]) return;
+    var referencePosition = new Vec3(location.x, location.y, location.z);
+    var directionVector = directionToVector[direction];
+    var position = referencePosition.plus(directionVector);
+
+    var item= items[heldItem.blockId];
+    if(item.name=="flint_and_steel")
+      player.use_flint_and_steel(referencePosition,directionVector);
+  });
+
+  player.use_flint_and_steel=async (referencePosition,direction) => {
+    let block=await player.world.getBlock(referencePosition);
+    if(block.name=="obsidian")
+    {
+      var frames=await detectFrame(player.world,referencePosition,direction);
+      if(frames.length==0)
+        return;
+      var air=getAir(frames[0]);
+      air.forEach(pos => player.setBlock(pos,81,0))
+    }
+  };
+};
+var directionToVector=[new Vec3(0,-1,0),new Vec3(0,1,0),new Vec3(0,0,-1),new Vec3(0,0,1),new Vec3(-1,0,0),new Vec3(1,0,0)];
\ No newline at end of file
diff --git a/src/lib/portal_detector.js b/src/lib/portal_detector.js
new file mode 100644
index 0000000..ca79c61
--- /dev/null
+++ b/src/lib/portal_detector.js
@@ -0,0 +1,87 @@
+var Vec3 = require("vec3").Vec3;
+var assert = require('assert');
+var flatMap = require('flatmap');
+var range = require('range').range;
+
+module.exports={detectFrame,findPotentialLines,findBorder,getAir};
+
+async function findLineInDirection(world,startingPoint,type,direction,directionV)
+{
+  var line=[];
+  var point=startingPoint;
+  while((await world.getBlock(point)).name==type && (await world.getBlockType(point.plus(directionV)))==0)
+  {
+    line.push(point);
+    point=point.plus(direction);
+  }
+  return line;
+}
+
+async function findLine(world,startingPoint,type,direction,directionV)
+{
+  var firstSegment=(await findLineInDirection(world,startingPoint.plus(direction.scaled(-1)),type,direction.scaled(-1),directionV)).reverse();
+  var secondSegment=await findLineInDirection(world,startingPoint,type,direction,directionV);
+  return firstSegment.concat(secondSegment);
+}
+
+
+async function findPotentialLines(world,startingPoint,directionV)
+{
+  var firstLineDirection=directionV.y!=0 ? [new Vec3(1,0,0),new Vec3(0,0,1)] :
+    [new Vec3(0,1,0)];
+  return (await Promise.all(firstLineDirection
+    .map(async d => ({direction:d,line:(await findLine(world,startingPoint,'obsidian',d,directionV))}))))
+    .filter(line => (line.line.length>=3 && line.direction.y!=0) ||
+    (line.line.length>=2 && line.direction.y==0));
+}
+
+function positiveOrder(line,direction)
+{
+  if(direction.x==-1 || direction.y==-1 || direction.z==-1)
+    return line.reverse();
+  return line;
+}
+
+async function findBorder(world,{line,direction},directionV)
+{
+  var bottom=line;
+  if(bottom.length==0)
+    return [];
+  var left=await findLineInDirection(world,bottom[0].plus(direction.scaled(-1).plus(directionV)),'obsidian',directionV,direction);
+  var right=await findLineInDirection(world,bottom[line.length-1].plus(direction).plus(directionV),'obsidian',
+    directionV,direction);
+  if(left.length!=right.length)
+    return null;
+  var top=await findLineInDirection(world,left[left.length-1].plus(direction).plus(directionV),'obsidian',
+    direction,directionV);
+  if(bottom.length!=top.length)
+    return null;
+  left=positiveOrder(left,directionV);
+  right=positiveOrder(right,directionV);
+  top=positiveOrder(top,direction);
+
+
+  if(direction.y!=0)
+    [bottom,left,right,top]=[left,bottom,top,right];
+
+  [bottom,top]=directionV.y<0 ? [top,bottom] : [bottom,top];
+  var horDir=direction.x!=0 || directionV.x!=0 ? 'x' :'z';
+  [left,right]=direction[horDir]<0 || directionV[horDir]<0 ? [right,left] : [left,right];
+
+  return [bottom,left,right,top];
+}
+
+async function detectFrame(world,startingPoint,directionV)
+{
+  let potentialLines=await findPotentialLines(world,startingPoint,directionV);
+
+  return (await Promise.all(potentialLines
+    .map(line => findBorder(world,line,directionV))))
+    .filter(border => border!=null);
+}
+
+function getAir(border)
+{
+  var [bottom,,,top]=border;
+  return flatMap(bottom,pos => range(1,top[0].y-bottom[0].y).map(i => pos.offset(0,i,0)));
+}
\ No newline at end of file
diff --git a/test/portal_detector.js b/test/portal_detector.js
new file mode 100644
index 0000000..aaead4c
--- /dev/null
+++ b/test/portal_detector.js
@@ -0,0 +1,148 @@
+var {detectFrame,findPotentialLines,findBorder,getAir}=require("flying-squid").portal_detector;
+var World = require('prismarine-world');
+var Chunk = require('prismarine-chunk')(require("flying-squid").version);
+var Vec3 = require("vec3").Vec3;
+var assert = require('assert');
+
+
+describe("Detect portal", function() {
+
+
+
+  var bottom=[new Vec3(3, 1, 1), new Vec3(4, 1, 1)];
+  var left=[new Vec3(2, 2, 1), new Vec3(2, 3, 1), new Vec3(2, 4, 1)];
+  var right=[new Vec3(5, 2, 1), new Vec3(5, 3, 1), new Vec3(5, 4, 1)];
+  var top=[new Vec3(3, 5, 1), new Vec3(4, 5, 1)];
+  var expectedBorder=[
+    bottom,
+    left,
+    right,
+    top
+  ];
+  var air=[new Vec3(3, 2, 1),new Vec3(3, 3, 1),new Vec3(3, 4, 1),new Vec3(4, 2, 1),new Vec3(4, 3, 1),new Vec3(4, 4, 1)];
+
+  var world;
+  before(function(){
+    world=new World();
+    var chunk=new Chunk();
+
+    expectedBorder.forEach(border => border.forEach(pos => chunk.setBlockType(pos,49)));
+    air.forEach(pos => chunk.setBlockType(pos,0));
+
+    return world.setColumn(0,0,chunk);
+  });
+
+
+  describe("detect potential first lines",function(){
+    it("detect potential first lines from bottom left", async function() {
+      let potentialLines=await findPotentialLines(world,bottom[0],new Vec3(0,1,0));
+      assert.deepEqual(potentialLines,[
+        {
+          "direction": new Vec3(1,0,0),
+          "line": bottom
+        }
+      ]);
+    });
+
+    it("detect potential first lines from bottom right", async function() {
+      let potentialLines=await findPotentialLines(world,bottom[bottom.length-1],new Vec3(0,1,0));
+      assert.deepEqual(potentialLines,[
+        {
+          "direction": new Vec3(1,0,0),
+          "line": bottom
+        }
+      ]);
+    });
+
+
+    it("detect potential first lines from top left", async function() {
+      let potentialLines=await findPotentialLines(world,top[0],new Vec3(0,-1,0));
+      assert.deepEqual(potentialLines,[
+        {
+          "direction": new Vec3(1,0,0),
+          "line": top
+        }
+      ]);
+    });
+
+    it("detect potential first lines from top right", async function() {
+      let potentialLines=await findPotentialLines(world,top[top.length-1],new Vec3(0,-1,0));
+      assert.deepEqual(potentialLines,[
+        {
+          "direction": new Vec3(1,0,0),
+          "line": top
+        }
+      ]);
+    });
+
+    it("detect potential first lines from left top", async function() {
+      let potentialLines=await findPotentialLines(world,left[left.length-1],new Vec3(1,0,0));
+      assert.deepEqual(potentialLines,[
+        {
+          "direction": new Vec3(0,1,0),
+          "line": left
+        }
+      ]);
+    });
+
+    it("detect potential first lines from right bottom", async function() {
+      let potentialLines=await findPotentialLines(world,right[0],new Vec3(-1,0,0));
+      assert.deepEqual(potentialLines,[
+        {
+          "direction": new Vec3(0,1,0),
+          "line": right
+        }
+      ]);
+    });
+  });
+
+
+  describe("find borders",function() {
+    it("find borders from bottom", async function () {
+      var border = await findBorder(world, {
+        "direction": new Vec3(1, 0, 0),
+        "line": bottom
+      }, new Vec3(0, 1, 0));
+      assert.deepEqual(border, expectedBorder)
+    });
+
+    it("find borders from top", async function () {
+      var border = await findBorder(world, {
+        "direction": new Vec3(1, 0, 0),
+        "line": top
+      }, new Vec3(0, -1, 0));
+      assert.deepEqual(border, expectedBorder)
+    });
+
+    it("find borders from left", async function () {
+      var border = await findBorder(world, {
+        "direction": new Vec3(0, 1, 0),
+        "line": left
+      }, new Vec3(1, 0, 0));
+      assert.deepEqual(border, expectedBorder)
+    });
+    it("find borders from right", async function () {
+      var border = await findBorder(world, {
+        "direction": new Vec3(0, 1, 0),
+        "line": right
+      }, new Vec3(-1, 0, 0));
+      assert.deepEqual(border, expectedBorder)
+    });
+  });
+
+  describe("detect portals",function(){
+    it("detect portals from bottom left",async function() {
+      var portals=await detectFrame(world,bottom[0],new Vec3(0,1,0));
+      assert.deepEqual(portals,[expectedBorder])
+    });
+    it("detect portals from right top",async function() {
+      var portals=await detectFrame(world,right[right.length-1],new Vec3(-1,0,0));
+      assert.deepEqual(portals,[expectedBorder])
+    })
+  });
+
+  it("get air",function(){
+    var foundAir=getAir(expectedBorder);
+    assert.deepEqual(foundAir,air);
+  });
+});