I haven't played this since I upgraded to El Capitan. It crashed when I start it, here is the message from the problem report:
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 libsystem_platform.dylib 0x91453254 _os_lock_corruption_abort + 0
1 libsystem_pthread.dylib 0x95f2da4f pthread_mutex_destroy + 23
2 SDL 0x3003ca4a SDL_DestroyMutex + 22
3 SDL 0x30005c97 SDL_GetAppState + 731
4 SDL 0x3002a625 SDL_VideoQuit + 33
5 SDL 0x3002f55c SDL_QuitSubSystem + 69
6 SDL 0x3002f5f1 SDL_Quit + 18
7 SDL 0x3002f24a SDL_GetError + 71
8 libsystem_platform.dylib 0x9145079b _sigtramp + 43
9 ??? 0xffffffff 0 + 4294967295
10 SDL 0x3002f22b SDL_GetError + 40
11 SDL 0x3002a6a8 SDL_VideoQuit + 164
12 SDL 0x3002f55c SDL_QuitSubSystem + 69
13 SDL 0x3002f5f1 SDL_Quit + 18
14 SDL 0x3002f24a SDL_GetError + 71
15 libsystem_platform.dylib 0x9145079b _sigtramp + 43
16 ??? 0xffffffff 0 + 4294967295
17 SDL 0x3002f22b SDL_GetError + 40
18 SDL 0x30008e61 SDL_AddTimer + 788
19 SDL 0x300276b0 SDL_UpperBlit + 516
20 net.sourceforge.meandmyshadow 0x00017287 0x1000 + 90759
21 net.sourceforge.meandmyshadow 0x000832c3 0x1000 + 533187
22 net.sourceforge.meandmyshadow 0x000706d8 0x1000 + 456408
23 net.sourceforge.meandmyshadow 0x000024cf 0x1000 + 5327
24 com.apple.Foundation 0x9db248a2 __57-[NSNotificationCenter addObserver:selector:name:object:]_block_invoke_2 + 50
25 com.apple.CoreFoundation 0x97b075a4 __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 20
26 com.apple.CoreFoundation 0x97b0752b ___CFXRegistrationPost_block_invoke + 75
27 com.apple.CoreFoundation 0x97b0749c _CFXRegistrationPost + 460
28 com.apple.CoreFoundation 0x97b071d6 ___CFXNotificationPost_block_invoke + 54
29 com.apple.CoreFoundation 0x97ac0b53 -[_CFXNotificationRegistrar find:object:observer:enumerator:] + 1715
30 com.apple.CoreFoundation 0x97abfd72 _CFXNotificationPost + 626
31 com.apple.Foundation 0x9dad6954 -[NSNotificationCenter postNotificationName:object:userInfo:] + 92
32 com.apple.AppKit 0x96cd2528 -[NSApplication _postDidFinishNotification] + 436
33 com.apple.AppKit 0x96cd21d6 -[NSApplication _sendFinishLaunchingNotification] + 249
34 com.apple.AppKit 0x96b7ca2a -[NSApplication(NSAppleEventHandling) _handleAEOpenEvent:] + 783
35 com.apple.AppKit 0x96b7c380 -[NSApplication(NSAppleEventHandling) _handleCoreEvent:withReplyEvent:] + 291
36 libobjc.A.dylib 0x9a74f5ac -[NSObject performSelector:withObject:withObject:] + 84
37 com.apple.Foundation 0x9db28180 __76-[NSAppleEventManager setEventHandler:andSelector:forEventClass:andEventID:]_block_invoke + 118
38 com.apple.Foundation 0x9db27cd7 -[NSAppleEventManager dispatchRawAppleEvent:withRawReply:handlerRefCon:] + 451
39 com.apple.Foundation 0x9db27ad2 _NSAppleEventManagerGenericHandler + 211
40 com.apple.AE 0x9a68ae54 aeDispatchAppleEvent(AEDesc const*, AEDesc*, unsigned long, unsigned char*) + 595
41 com.apple.AE 0x9a687b75 dispatchEventAndSendReply(AEDesc const*, AEDesc*) + 44
42 com.apple.AE 0x9a687a88 aeProcessAppleEvent + 299
43 com.apple.HIToolbox 0x98886c5a AEProcessAppleEvent + 55
44 com.apple.AppKit 0x96b77ca8 _DPSNextEvent + 2415
45 com.apple.AppKit 0x96b76cd0 -[NSApplication _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 1057
46 com.apple.AppKit 0x96b768a7 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 121
47 com.apple.AppKit 0x96b6a01b -[NSApplication run] + 1063
48 net.sourceforge.meandmyshadow 0x00002c4c 0x1000 + 7244
49 net.sourceforge.meandmyshadow 0x000022a5 0x1000 + 4773
I hope this helps and you're able to fix it. My kids love playing this game.
Thanks.