I can't find any manual on the net, but this is what I figured out:
CTRL+K for keyboard, S/F for left right, D for stop, E/C for factory speed up/down, Return for crosshairs, Space for flip valves CTRL+J for joystick, button 2 for crosshairs, button 1 to flip valves.
When an exploding gumball shows up there's a warning sound, locate the bomb, bring up the crosshairs and put the crosshairs in contact with the bomb and it will be zapped.
The exploding gumballs don't show up until Thursday.
The crosshairs initially appear over the corkscrew so if you can make the bomb go up the corkscrew you can just activate the crosshairs. There's also a flashing countdown timer for the bomb in the upper left and you may be able to wait for it to go up the corkscrew.
A pretty good strategy is to use the left chutes as much as possible early on as you can clear the gumball out quickly. If you let it take the long path you have to keep an eye on it and it gets hard to track it with the incoming gumballs. You have to ramp up the speed to keep up with the quota, but don't set it too high that you make mistakes and see the quota get bigger.
I figured out the difference between illegal and illegal2 handlers: the logerror print message for the former prints 1 byte for opcode, and the latter prints 2. This means the mistake in the prefix 40 table was effectively completely harmless, just making some error messages in MAME slightly wrong.
I thought the first longer morphing CGI movie was this:
John Whitney - Arabesque (1975) early computer graphics
In Germany in 1970th/80th there was a famous family gameshow "Die Montagsmaler" (The Monday's Painters), in that a person had to quickly draw an object (that he got told as a word) that other people had to guess before the timer runs up. The special thing was that instead of a chalkboard it employed one of the very first lightpen computers named "Telestrator" that apparently got fed with a punchcard to display to the spectators the word of the object to be guessed. While nowadays tablet computers with touchscreen and pen are common, until 1980th it was very unusual to draw directly on screen, and the show was such famous that in Germany until 1990th everybody associated the use of a lightpen (on C64 etc.) with Montagsmaler (much like in Britain the appearance of a police box got associated with the TARDIS of Doctor Who). Kids at schools often played the game during break/recess on the classroom blackboard.
I tried hard to find out how this primitive graphical "computer" worked. Apparently it used a persistent vector monitor CRT similar like an analogue storage oscilloscope filmed by a TV camera, and the ticking clock dot frame around the screen likely was just a kind of B/W luma-key effect (greenscreen predecessor) superimposing the picture of a clock made from lightbulbs and relays (and a contact wheel?) with the filmed vector screen. Telestrators were originally used in USA mainly to comment sports on TV for marking the position of players and ball etc. and were invented already in 1950th.
Here are some patents (websearch the numbers) I found about related hardware:
Telestrator_writing pickup_US2986596.pdf Telestrator_superimposed dynamic tv_US3617630.pdf Telestrator_electronic pointer for tv images (lightpen)_US2487641.pdf Telestrator_AV teaching system&response_US3718759.pdf teaching system with tv receiver_US3671668.pdf optical graphic data tablet_US3761877.pdf multiple camera superimposed message_US3580993.pdf lightpen_telewriting apparatus_US3089918.pdf lightpen_operation on remote computer_US3543240.pdf lightpen_electron beam sensor_US3413515.pdf computer graphic using video phone_US3584142.pdf