Put the summary of the bug you're having here

I keep crashing when trying to play the game. I get this error when clicking on my world. I was on the latest version and kept crashing. I uninstalled and reinstalled but kept crashing. I then went down to a lower level and now crash as well. Extremely disappointed with this game-it never works and there are no good solutions.
Minecraft Crash Report ----
// I just don't know what went wrong

Time: 2/21/15 6:06 PM
Description: Starting integrated server

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING at line 1 column 1
at com.google.gson.Gson.fromJson(Gson.java:815)
at com.google.gson.Gson.fromJson(Gson.java:768)
at ns.b(SourceFile:156)
at ns.<init>(SourceFile:42)
at net.minecraft.server.MinecraftServer.<init>(SourceFile:114)
at bsx.<init>(SourceFile:38)
at bao.a(SourceFile:1610)
at bdx.e(SourceFile:162)
at bdx.a(SourceFile:127)
at bdw.a(SourceFile:172)
at bdw.k(SourceFile:232)
at bdw.p(SourceFile:211)
at bao.p(SourceFile:1328)
at bao.ak(SourceFile:774)
at bao.f(SourceFile:728)
at net.minecraft.client.main.Main.main(SourceFile:148)
Caused by: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING at line 1 column 1
at com.google.gson.stream.JsonReader.beginArray(JsonReader.java:338)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:79)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:60)
at com.google.gson.Gson.fromJson(Gson.java:803)
... 15 more

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

– Head –
Stacktrace:
at com.google.gson.Gson.fromJson(Gson.java:815)
at com.google.gson.Gson.fromJson(Gson.java:768)
at ns.b(SourceFile:156)
at ns.<init>(SourceFile:42)
at net.minecraft.server.MinecraftServer.<init>(SourceFile:114)
at bsx.<init>(SourceFile:38)

– Starting integrated server –
Details:
Level ID: camp half blood
Level Name: camp half blood
Stacktrace:
at bao.a(SourceFile:1610)
at bdx.e(SourceFile:162)
at bdx.a(SourceFile:127)
at bdw.a(SourceFile:172)
at bdw.k(SourceFile:232)
at bdw.p(SourceFile:211)

– Affected screen –
Details:
Screen name: bee
Stacktrace:
at bao.p(SourceFile:1328)
at bao.ak(SourceFile:774)
at bao.f(SourceFile:728)
at net.minecraft.client.main.Main.main(SourceFile:148)

– System Details –
Details:
Minecraft Version: 1.7.10
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 144249976 bytes (137 MB) / 186109952 bytes (177 MB) up to 1060372480 bytes (1011 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Launched Version: 1.7.10
LWJGL: 2.9.1
OpenGL: Intel(R) HD Graphics GL version 2.1.0 - Build 8.15.10.2202, Intel
GL Caps: Using GL 1.3 multitexturing.
Using framebuffer objects because EXT_framebuffer_object is supported.
Anisotropic filtering is supported and maximum anisotropy is 2.
Shaders are available because OpenGL 2.1 is supported.

Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Anisotropic Filtering: Off (1)