Game 3 Unit 2 of 6 1 hr learning time

An Unknown Wait

A fixed beat can be learnt, and a reaction test you can predict is no test. Make the wait a different length every run with RND — now the flash always catches you off guard.

33% of Reflex

There's a flaw in the last version: the wait is always the same. Run it a few times and your finger learns the rhythm — you're hitting the key on a count, not on the flash. A real reaction test has to catch you off guard. So make the wait a different length every single run.

10 PRINT CHR$(147)
20 POKE 53281,0
30 PRINT "WATCH THE SCREEN..."
40 W=INT(RND(1)*120)+60
50 FOR T=1 TO W*8:NEXT T
60 POKE 53281,1
A C64 screen, fully black, showing WATCH THE SCREEN at the top — the tense wait before the flash.
The waiting state: black, holding, no telling how long. The flash could come in half a second or in three — and that not-knowing is the whole game.

Line 40 is the new part: W=INT(RND(1)*120)+60. RND(1) hands back a fraction between 0 and 1; multiply by 120 and you have a number from 0 up to 120; INT throws the decimals away to leave a whole number; +60 shifts the range so it never drops below 60. So W lands somewhere between 60 and 180, fresh each run.

Then line 50 uses it: FOR T=1 TO W*8:NEXT T. The loop's length now depends on W, so the wait stretches and shrinks from one run to the next. You can't count it out any more — you can only watch, and react. That uncertainty is tension, and RND is where it comes from.

Try this

  • Widen the odds. Change 120 to 240 and the wait can run much longer — the tension stretches with it.
  • Never too quick. The +60 sets the shortest possible wait. Raise it to +120 and even the fastest flash gives you a moment to settle.

What's next

The flash now comes when you least expect it — but the program still doesn't know how fast you answered it. In Unit 3 you meet the C64's clock, TI, and start measuring the gap between the flash and your key.