resolve conflicts

.gitignore

@@ -10,3 +10,4 @@ public/
 build/
 .tmp
 .idea/
+/.vs/

en/3/02-ownable.md

@@ -189,7 +189,7 @@ To handle cases like this, one common practice that has emerged is to make contr
 
 ## OpenZeppelin's `Ownable` contract
 
-Below is the `Ownable` contract taken from the **_OpenZeppelin_** Solidity library. OpenZeppelin is a library of secure and community-vetted smart contracts that you can use in your own DApps. After this lesson, while you anxiously await the release of Lesson 4, we highly recommend you check out their site to further your learning!
+Below is the `Ownable` contract taken from the **_OpenZeppelin_** Solidity library. OpenZeppelin is a library of secure and community-vetted smart contracts that you can use in your own DApps. After this lesson, we highly recommend you check out their site to further your learning!
 
 Give the contract below a read-through. You're going to see a few things we haven't learned yet, but don't worry, we'll talk about them afterward.
 

en/3/08-functionmodifiers.md

@@ -188,7 +188,7 @@ mapping (uint => uint) public age;
 
 // Modifier that requires this user to be older than a certain age:
 modifier olderThan(uint _age, uint _userId) {
-  require (age[_userId] >= _age);
+  require(age[_userId] >= _age);
   _;
 }
 

en/4/battle-02.md

@@ -7,6 +7,8 @@ material:
     language: sol
     startingCode:
       "zombieattack.sol": |
+        pragma solidity ^0.4.19;
+
         import "./zombiehelper.sol";
 
         contract ZombieBattle is ZombieHelper {
@@ -203,6 +205,8 @@ material:
 
         }
     answer: >
+      pragma solidity ^0.4.19;
+
       import "./zombiehelper.sol";
 
       contract ZombieBattle is ZombieHelper {

en/4/battle-03.md

@@ -7,6 +7,8 @@ material:
     language: sol
     startingCode:
       "zombieattack.sol": |
+        pragma solidity ^0.4.19;
+
         import "./zombiehelper.sol";
 
         contract ZombieBattle is ZombieHelper {
@@ -211,6 +213,8 @@ material:
 
         }
     answer: >
+      pragma solidity ^0.4.19;
+
       import "./zombiehelper.sol";
 
       contract ZombieBattle is ZombieHelper {

en/4/battle-04.md

@@ -66,6 +66,8 @@ material:
           }
         }
       "zombieattack.sol": |
+        pragma solidity ^0.4.19;
+
         import "./zombiehelper.sol";
 
         contract ZombieBattle is ZombieHelper {

en/4/battle-05.md

@@ -59,6 +59,8 @@ material:
 
         }
       "zombieattack.sol": |
+        pragma solidity ^0.4.19;
+
         import "./zombiehelper.sol";
 
         contract ZombieBattle is ZombieHelper {
@@ -238,6 +240,11 @@ material:
         function setLevelUpFee(uint _fee) external onlyOwner {
           levelUpFee = _fee;
         }
+        
+        function levelUp(uint _zombieId) external payable {
+          require(msg.value == levelUpFee);
+          zombies[_zombieId].level++;
+        }
 
         function changeName(uint _zombieId, string _newName) external aboveLevel(2, _zombieId) ownerOf(_zombieId) {
           zombies[_zombieId].name = _newName;

en/4/battle-06.md

@@ -7,6 +7,8 @@ material:
     language: sol
     startingCode:
       "zombieattack.sol": |
+        pragma solidity ^0.4.19;
+
         import "./zombiehelper.sol";
 
         contract ZombieBattle is ZombieHelper {
@@ -216,6 +218,8 @@ material:
 
         }
     answer: >
+      pragma solidity ^0.4.19;
+
       import "./zombiehelper.sol";
 
       contract ZombieBattle is ZombieHelper {

en/4/battle-07.md

@@ -54,6 +54,8 @@ material:
 
         }
       "zombieattack.sol": |
+        pragma solidity ^0.4.19;
+
         import "./zombiehelper.sol";
 
         contract ZombieBattle is ZombieHelper {

en/4/battle-08.md

@@ -7,6 +7,8 @@ material:
     language: sol
     startingCode:
       "zombieattack.sol": |
+        pragma solidity ^0.4.19;
+
         import "./zombiehelper.sol";
 
         contract ZombieBattle is ZombieHelper {
@@ -220,6 +222,8 @@ material:
 
         }
     answer: >
+      pragma solidity ^0.4.19;
+
       import "./zombiehelper.sol";
 
       contract ZombieBattle is ZombieHelper {

en/4/battle-09.md

@@ -7,6 +7,8 @@ material:
     language: sol
     startingCode:
       "zombieattack.sol": |
+        pragma solidity ^0.4.19;
+
         import "./zombiehelper.sol";
 
         contract ZombieBattle is ZombieHelper {
@@ -225,6 +227,8 @@ material:
 
         }
     answer: >
+      pragma solidity ^0.4.19;
+
       import "./zombiehelper.sol";
 
       contract ZombieBattle is ZombieHelper {

en/5/00-overview.md

@@ -0,0 +1,13 @@
+---
+title: ERC721 & Crypto-Collectibles
+header: "Lesson 5: ERC721 & Crypto-Collectibles"
+roadmap: roadmap5.jpg
+---
+
+Whew! Things are starting to heat up in here...
+
+In this lesson, we're going to get a bit more advanced.
+
+We're going to talk about **tokens**, the **ERC721** standard, and **crypto-collectible assets**.
+
+In other words, we're going to **make it so you can trade your zombies with your friends.**