10-05-2022, 01:37 AM
Okay, so now will demo the "flow through" for the alien space ships by adding yet another timer to the mix, and some keys to press to speed up or slow down the action.
Press or hold the left Ctrl key to speed it up, the right Alt key to slow things down. Press something else like an arrow key to make a tiny sound. Why? Just to show how the player has a lot of input while everything around the screen is moving. That's what I mean by designing a game to have a "flow through" structure.
Stage 4)
Next up, how about we see what happens when those idiot aliens run into each other?
Pete
Press or hold the left Ctrl key to speed it up, the right Alt key to slow things down. Press something else like an arrow key to make a tiny sound. Why? Just to show how the player has a lot of input while everything around the screen is moving. That's what I mean by designing a game to have a "flow through" structure.
Stage 4)
Code: (Select All)
DIM SHARED top, bottom, left, right, s_delay
a = 120: b = 42
WIDTH a, b
_SCREENMOVE 0, 0
top = 3: bottom = _HEIGHT: left = 0: right = _WIDTH
msg$ = "Alien space ship movement demo."
LOCATE 1, (right - left) \ 2 - LEN(msg$) \ 2
PRINT msg$;
LOCATE 1, 2: PRINT STRING$(_WIDTH, "_");
s_delay = 100
DO
_LIMIT 30
IF _KEYDOWN(100306) THEN IF s_delay - 5 > 0 THEN s_delay = s_delay - 5: LOCATE 1, 2: PRINT "Speed delay ="; s_delay / 100; " ";
IF _KEYDOWN(100308) THEN IF s_delay < 500 THEN s_delay = s_delay + 5: LOCATE 1, 2: PRINT "Speed delay ="; s_delay / 100; " ";
IF LEN(INKEY$) THEN SOUND 1000, .1
alien_move
LOOP
SUB alien_move:
STATIC a_y(5), a_x(5), olda_y(5), olda_x(5), inertia(5), ran(5), ran_y(5), ran_x(5), oldran(5), z5, z6, itr, alien_ship_max
IF alien$ = "" THEN alien$ = "-<>-": alien_ship_max = 5 ' Initiate.
IF ABS(z5 - TIMER) > s_delay / 1000 THEN ' Time delay.
DO
itr = itr + 1: IF itr > alien_ship_max THEN itr = 1 ' Needed to offset the EXIT DO hover event, which on exit does not affect the itr variable.
y_restore = CSRLIN: x_restore = POS(0) ' Restore column and row upon exit.
IF olda_y(itr) <> 0 AND olda_x(itr) <> 0 THEN LOCATE olda_y(itr), olda_x(itr): PRINT SPACE$(LEN(alien$));
IF inertia(itr) = 0 THEN
inertia(itr) = INT(RND * (bottom - top) / 2) + 1 ' How many moves to go in any one direction.
ran(itr) = INT(RND * 8) + 1 ' Choose 1 of 8 possible directions.
IF ran(itr) = oldran(itr) OR olda_y(itr) = 0 AND olda_x(itr) = 0 AND ran = 1 OR olda_y(itr) = 0 AND olda_x(itr) = 0 AND ran = 5 THEN
EXIT DO ' Just hover if direction was not changed on existing alien space ship or if a new alien space ship is entering from the sides and up or down was generated.
END IF
SELECT CASE ran(itr) ' Get changes in column and row coordinates.
CASE 1: ran_y(itr) = -1: ran_x(itr) = 0 ' Up.
CASE 2: ran_y(itr) = -1: ran_x(itr) = 1 ' Up and right.
CASE 3: ran_y(itr) = 0: ran_x(itr) = 1 ' Right.
CASE 4: ran_y(itr) = 1: ran_x(itr) = 1 ' Down and right.
CASE 5: ran_y(itr) = 1: ran_x(itr) = 0 ' Down.
CASE 6: ran_y(itr) = 1: ran_x(itr) = -1 ' Down and left.
CASE 7: ran_y(itr) = 0: ran_x(itr) = -1 ' Left.
CASE 8: ran_y(itr) = -1: ran_x(itr) = -1 ' Up and left.
END SELECT
IF olda_y(itr) = 0 AND olda_x(itr) = 0 THEN ' New alien space ship enters the screen.
a_y(itr) = (bottom - top) \ 2: a_x(itr) = (right - left) \ 2 ' Center sreen.
a_y(itr) = (bottom - top) \ 4 + RND * (bottom - top) \ 4
IF ran(itr) < 5 THEN ' Determine side of entry from initial direction.
a_x(itr) = left + 1 ' Enter from the left side and go right.
ELSE
a_x(itr) = right - LEN(alien$) ' Enter from the right side and go left.
END IF
END IF
oldran(itr) = ran(itr) ' Remember last direction. Another line uses this to disallow any RND that chooses the same direction twice.
ELSE
inertia(itr) = inertia(itr) - 1 ' Count down the number of moves in any one direction. When zero, switch direction.
END IF
a_y(itr) = a_y(itr) + ran_y(itr): a_x(itr) = a_x(itr) + ran_x(itr) * 2 ' Next move coordinates. I use * 2 for horizontal movement to match the 16x8 pixel height over width factor.
IF a_y(itr) < top OR a_y(itr) > bottom OR a_x(itr) <= left OR a_x(itr) + LEN(alien$) > right THEN
olda_x(itr) = 0: olda_y(itr) = 0: inertia(itr) = 0: oldran(itr) = 0 ' Out of bounds and off the screen.
ELSE
LOCATE a_y(itr), a_x(itr): PRINT alien$; ' Move alien space ship.
olda_y(itr) = a_y(itr): olda_x(itr) = a_x(itr) ' Remember these coordinates to erase alien space ship on next loop.
END IF
IF itr = alien_ship_max THEN itr = 0: EXIT DO
IF ABS(z6 - TIMER) > s_delay / 2 THEN skipz5 = -1: EXIT DO
LOOP
IF skipz5 = 0 THEN z5 = TIMER
z6 = TIMER
LOCATE y_restore, x_restore ' Restore entry column and row positions.
END IF
END SUBNext up, how about we see what happens when those idiot aliens run into each other?
Pete