Light is rendered as if it was 15 everywhere, but in the debug screen, it appears correctly in caves, but at night and outdoor the debug screen also shows 15. However, mobs still spawn.

Report made by a forced crash:

---- Minecraft Crash Report ----
// This is a token for 1 free hug. Redeem at your nearest Mojangsta: _HUG~

Time: 2016.01.26. 19:25
Description: Manually triggered debug crash

java.lang.Throwable
at bcc.ay(SourceFile:1682)
at bcc.s(SourceFile:1603)
at bcc.au(SourceFile:949)
at bcc.a(SourceFile:390)
at net.minecraft.client.main.Main.main(SourceFile:122)

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

– Head –
Stacktrace:
at bcc.ay(SourceFile:1682)

– Affected level –
Details:
Level name: MpServer
All players: 1 total; [bmp['Asztro2'/38386, l='MpServer', x=-365,80, y=61,00, z=233,06]]
Chunk stats: MultiplayerChunkCache: 1089, 1089
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (-44,64,248), Chunk: (at 4,4,8 in -3,15; contains blocks -48,0,240 to -33,255,255), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Level time: 5987776 game time, 7269885 day time
Level dimension: 0
Level storage version: 0x00000 - Unknown?
Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Forced entities: 111 total; [bmp['Asztro2'/38386, l='MpServer', x=-365,80, y=61,00, z=233,06], we['Tintahal'/39691, l='MpServer', x=-429,82, y=62,37, z=192,57], we['Tintahal'/39693, l='MpServer', x=-430,49, y=61,00, z=187,40], we['Tintahal'/39694, l='MpServer', x=-429,19, y=60,65, z=193,71], ze['Csontváz'/39702, l='MpServer', x=-371,69, y=58,63, z=230,63], vv['Csirke'/38462, l='MpServer', x=-432,25, y=67,00, z=277,22], zi['Zombi'/38464, l='MpServer', x=-441,53, y=65,00, z=270,72], vv['Csirke'/38466, l='MpServer', x=-433,81, y=62,63, z=308,75], yq['Creeper'/39752, l='MpServer', x=-338,50, y=64,00, z=159,50], ze['Csontváz'/39754, l='MpServer', x=-336,50, y=64,00, z=164,50], wc['Bárány'/38478, l='MpServer', x=-430,53, y=75,00, z=168,72], wc['Bárány'/38479, l='MpServer', x=-419,06, y=62,66, z=179,94], yq['Creeper'/39761, l='MpServer', x=-379,50, y=64,00, z=182,50], wc['Bárány'/38482, l='MpServer', x=-417,56, y=68,00, z=243,25], yq['Creeper'/39762, l='MpServer', x=-376,50, y=64,00, z=179,50], vv['Csirke'/38483, l='MpServer', x=-426,88, y=67,00, z=276,50], yq['Creeper'/39763, l='MpServer', x=-372,50, y=64,00, z=180,50], zf['Nyálka'/38485, l='MpServer', x=-427,34, y=68,25, z=297,91], zg['Pók'/38486, l='MpServer', x=-419,50, y=69,00, z=303,50], zg['Pók'/39769, l='MpServer', x=-374,50, y=64,00, z=185,50], yq['Creeper'/38491, l='MpServer', x=-415,50, y=28,00, z=204,50], vs['Denevér'/39515, l='MpServer', x=-312,47, y=16,84, z=206,56], wc['Bárány'/38492, l='MpServer', x=-419,22, y=67,00, z=241,50], yq['Creeper'/39779, l='MpServer', x=-418,50, y=69,00, z=289,50], yq['Creeper'/39780, l='MpServer', x=-418,50, y=69,00, z=290,50], yq['Creeper'/39781, l='MpServer', x=-420,50, y=69,00, z=287,50], wc['Bárány'/38502, l='MpServer', x=-389,22, y=64,00, z=180,38], wb['Nyúl'/38503, l='MpServer', x=-394,50, y=65,00, z=186,34], ze['Csontváz'/38504, l='MpServer', x=-396,69, y=70,00, z=230,22], yq['Creeper'/38506, l='MpServer', x=-391,50, y=23,00, z=287,50], yq['Creeper'/38507, l='MpServer', x=-391,50, y=23,00, z=289,50], yq['Creeper'/38513, l='MpServer', x=-381,50, y=63,00, z=165,50], wc['Bárány'/38514, l='MpServer', x=-377,34, y=64,00, z=160,44], yq['Creeper'/38515, l='MpServer', x=-379,19, y=64,00, z=160,69], vs['Denevér'/38518, l='MpServer', x=-372,53, y=21,94, z=180,44], yq['Creeper'/38520, l='MpServer', x=-379,91, y=60,00, z=208,31], zi['Zombi'/38521, l='MpServer', x=-373,56, y=59,00, z=201,72], zi['Zombi'/38522, l='MpServer', x=-375,50, y=59,00, z=202,69], vs['Denevér'/38523, l='MpServer', x=-381,25, y=56,10, z=195,38], zi['Zombi'/38524, l='MpServer', x=-369,53, y=56,00, z=196,78], vs['Denevér'/39548, l='MpServer', x=-316,47, y=29,22, z=230,97], zi['Zombi'/38526, l='MpServer', x=-374,50, y=55,00, z=196,50], zi['Zombi'/38527, l='MpServer', x=-374,50, y=55,00, z=195,50], wc['Bárány'/38528, l='MpServer', x=-372,22, y=65,00, z=195,53], yq['Creeper'/38529, l='MpServer', x=-377,72, y=59,00, z=203,88], zi['Zombi'/38530, l='MpServer', x=-373,50, y=14,00, z=224,50], yc['item.item.sulphur'/38531, l='MpServer', x=-374,16, y=67,00, z=232,31], rw['Tapasztalati gömb'/38532, l='MpServer', x=-373,72, y=67,00, z=228,22], ze['Csontváz'/39556, l='MpServer', x=-366,31, y=63,81, z=229,28], rw['Tapasztalati gömb'/38533, l='MpServer', x=-374,25, y=67,00, z=225,81], rw['Tapasztalati gömb'/38534, l='MpServer', x=-373,75, y=67,00, z=226,97], rw['Tapasztalati gömb'/38535, l='MpServer', x=-368,25, y=65,00, z=233,12], rw['Tapasztalati gömb'/38536, l='MpServer', x=-368,25, y=65,00, z=233,10], rw['Tapasztalati gömb'/38537, l='MpServer', x=-368,25, y=65,00, z=233,12], zg['Pók'/38538, l='MpServer', x=-383,50, y=64,00, z=280,50], zi['Zombi'/38539, l='MpServer', x=-377,50, y=63,00, z=305,50], wi['Ló'/38549, l='MpServer', x=-365,00, y=66,00, z=238,16], yq['Creeper'/38550, l='MpServer', x=-359,50, y=68,00, z=276,50], wb['Nyúl'/38554, l='MpServer', x=-344,28, y=64,28, z=157,41], ze['Csontváz'/38555, l='MpServer', x=-351,25, y=68,00, z=252,44], wb['Nyúl'/38556, l='MpServer', x=-340,44, y=67,00, z=296,72], wb['Nyúl'/38558, l='MpServer', x=-332,81, y=64,00, z=159,84], wb['Nyúl'/38559, l='MpServer', x=-317,69, y=64,00, z=162,50], wc['Bárány'/38560, l='MpServer', x=-324,81, y=63,00, z=171,53], wb['Nyúl'/38561, l='MpServer', x=-320,81, y=63,00, z=169,34], zg['Pók'/38562, l='MpServer', x=-335,03, y=64,00, z=178,50], vw['Tehén'/38563, l='MpServer', x=-322,88, y=66,00, z=193,66], wb['Nyúl'/38564, l='MpServer', x=-320,59, y=67,00, z=205,53], wb['Nyúl'/38566, l='MpServer', x=-333,03, y=67,00, z=233,50], zg['Pók'/38567, l='MpServer', x=-333,25, y=68,00, z=252,75], vs['Denevér'/39591, l='MpServer', x=-315,25, y=27,69, z=225,25], wb['Nyúl'/38568, l='MpServer', x=-321,00, y=70,00, z=251,13], ze['Csontváz'/38582, l='MpServer', x=-310,53, y=67,00, z=169,34], ze['Csontváz'/38584, l='MpServer', x=-306,50, y=35,00, z=183,50], wb['Nyúl'/38586, l='MpServer', x=-316,41, y=64,00, z=181,50], yq['Creeper'/38587, l='MpServer', x=-305,81, y=65,00, z=186,53], zh['Boszorkány'/38588, l='MpServer', x=-314,50, y=40,00, z=207,50], zi['Zombi'/38589, l='MpServer', x=-309,50, y=41,00, z=196,50], zi['Zombi'/38590, l='MpServer', x=-311,50, y=41,00, z=194,50], yq['Creeper'/38591, l='MpServer', x=-312,53, y=68,00, z=202,16], wc['Bárány'/38592, l='MpServer', x=-319,25, y=68,00, z=214,53], wc['Bárány'/38593, l='MpServer', x=-319,84, y=68,00, z=227,81], wc['Bárány'/38594, l='MpServer', x=-308,16, y=72,00, z=269,53], wb['Nyúl'/38595, l='MpServer', x=-318,22, y=74,00, z=280,53], wb['Nyúl'/38596, l='MpServer', x=-316,63, y=74,00, z=277,66], wb['Nyúl'/38597, l='MpServer', x=-307,50, y=75,00, z=274,94], zg['Pók'/38598, l='MpServer', x=-304,94, y=76,00, z=298,81], ze['Csontváz'/38607, l='MpServer', x=-301,50, y=32,00, z=168,50], ze['Csontváz'/38608, l='MpServer', x=-297,56, y=30,00, z=171,25], zi['Zombi'/38609, l='MpServer', x=-309,47, y=64,00, z=178,22], yq['Creeper'/38610, l='MpServer', x=-302,50, y=67,00, z=195,50], ze['Csontváz'/38611, l='MpServer', x=-300,50, y=22,00, z=214,50], ze['Csontváz'/38612, l='MpServer', x=-300,50, y=22,00, z=215,50], yq['Creeper'/38614, l='MpServer', x=-292,50, y=22,00, z=217,50], yq['Creeper'/38615, l='MpServer', x=-305,19, y=76,00, z=285,84], yq['Creeper'/38616, l='MpServer', x=-300,81, y=76,00, z=289,38], zg['Pók'/38617, l='MpServer', x=-303,50, y=76,00, z=290,50], vs['Denevér'/39646, l='MpServer', x=-428,47, y=39,69, z=282,88], ze['Csontváz'/38626, l='MpServer', x=-287,72, y=64,00, z=157,41], vs['Denevér'/38627, l='MpServer', x=-298,91, y=36,22, z=177,25], ze['Csontváz'/39406, l='MpServer', x=-366,72, y=62,00, z=236,28], ze['Csontváz'/39407, l='MpServer', x=-366,31, y=62,00, z=236,69], zi['Zombi'/39663, l='MpServer', x=-341,50, y=67,00, z=229,50], ze['Csontváz'/39408, l='MpServer', x=-366,72, y=82,88, z=236,41], wh['Farkas'/38387, l='MpServer', x=-356,59, y=67,00, z=235,66], wh['Farkas'/38388, l='MpServer', x=-356,69, y=67,00, z=236,94], yc['item.item.rottenFlesh'/38389, l='MpServer', x=-352,59, y=67,00, z=234,19], rw['Tapasztalati gömb'/38390, l='MpServer', x=-354,19, y=66,00, z=229,75], rw['Tapasztalati gömb'/38391, l='MpServer', x=-352,59, y=66,00, z=228,28], rw['Tapasztalati gömb'/38392, l='MpServer', x=-352,94, y=66,00, z=229,75], ze['Csontváz'/38393, l='MpServer', x=-365,53, y=85,00, z=230,75]]
Retry entities: 0 total; []
Server brand: vanilla
Server type: Integrated singleplayer server
Stacktrace:
at bkq.a(SourceFile:365)
at bcc.b(SourceFile:2503)
at bcc.a(SourceFile:399)
at net.minecraft.client.main.Main.main(SourceFile:122)

– System Details –
Details:
Minecraft Version: 16w03a
Operating System: Windows 10 (x86) version 10.0
Java Version: 1.8.0_66, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 146580840 bytes (139 MB) / 523501568 bytes (499 MB) up to 523501568 bytes (499 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
Launched Version: 16w03a
LWJGL: 2.9.4
OpenGL: ATI Mobility Radeon HD 3400 Series GL version 3.3.11672 Compatibility Profile Context, ATI Technologies Inc.
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: Yes
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: Faithful 32x32 1.8
Current Language: Magyar (Magyarország)
Profiler Position: N/A (disabled)
CPU: 2x Intel(R) Core(TM)2 Duo CPU T5750 @ 2.00GHz