How to code efficiently

[Marcus]

Here are some modifications:

Code:

'=========================================================================
' Winter Christmas
' It's almost Christmas ! Santa Claus is running to the north pole.
' Please be careful, Yeti didn't like Santa Claus.
'
' Control keys
' - SPACE BAR = jump
' - DOWN      = slow down game speed
' - LEFT      = snow direction left to right
' - RIGHT    = snow direction right to left
'
' Resources
' - Slow motion effect by Marcus
'  https://naalaa.com/forum/thread-155-post-1124.html#pid1124
' - Wind moderate strong JPN by freesound community
'  https://pixabay.com/sound-effects/wind-moderate-strong-jpn-78086/
' - Yeti King sprite sheet submitter by madhattervx
'  https://www.spriters-resource.com/pc_computer/spelunky2/sheet/182550/
' - Santa Claus Sprite Sheet
'  https://www.gameart2d.com/santa-claus-free-sprites.html
'
'=========================================================================

'----------------
' INITIALIZATION
'----------------
#win32
set window "Winter Christmas", 512, 256,false,2
set redraw off

'color definition
deepblue = [20,30,40]
white    = [255,255,255]

visible j        'timer for snow direction 
visible direction 'snow direction
message = ""

' snow
snow = []
for i = 1 to 1000
    c = 64 + rnd(256)
    snow[sizeof(snow)] = [
            x: rnd(512), y: rnd(512),
            dy: 25 + rnd(200),
            c: [c, c, c],
            Update: function(dt,direction)
                this.y = (this.y + this.dy*dt)%230             
               
                if direction then
                    if this.x > 0 then
                        this.x = this.x - rnd(0,1)
                    else
                        this.x = 512
                    endif
                else
                    if this.x < 512 then
                        this.x = this.x + rnd(0,1)
                    else
                        this.x = 0
                    endif               
                endif
               
            endfunc,
            Draw: function()
                set color this.c
                draw pixel this.x, this.y
            endfunc]
next

' Game speed.
gameSpeed = 1

' Sound effect
wind = loadmusic("assets/wind1.wav")
play music wind,1

' Yeti
yeti = []
yeti.walk = loadimage("assets/yeti_walk.png",8,1)
yeti.cell = 0
yeti.move = 520

' Santa Claus
santa = []
santa.run = loadimage("assets/santaclaus.png",11,1)
santa.cell = 0
santa.move = -50
santa.jump = 175
santa.pos = 0 'santa position 0=stay 1=up 2=down
santa.deltay = 0


'--------------
' MAIN PROGRAM
'--------------
prevTime = clock()
while not keydown(KEY_ESCAPE)
    ' Delta time
    t = clock()
    dt = (min(t - prevTime, 66))/1000
    prevTime = t

    ' Slow down by pressing DOWN
    if keydown(KEY_DOWN)  then
        gameSpeed = max(gameSpeed - dt/5, 0.25)
    else 
        gameSpeed = min(gameSpeed + dt/5, 1)
    endif
    dt = dt*gameSpeed     
       
    set color deepblue ; cls                      'clear background
    set color white ; draw rect 0,220,512,10,1    'white ground

    'santa claus animation
    draw image santa.run,santa.move,santa.jump,santa.cell
    'if santa.cell<11 then
    '    santa.cell = santa.cell + dt*20
    'else
    '    santa.cell = 0
    'endif
    santa.cell = (santa.cell + dt*20)%11
    if santa.move > 520 then
        santa.move = -50
    else
        santa.move = santa.move + dt*50
    endif
    'if keydown(KEY_SPACE) then
    '    santa.pos = 1 'santa position 0=stay 1=up 2=down
    'endif
    'if santa.pos=1 then
    '    santa.jump = santa.jump - dt*100
    'elseif santa.pos=2 then
    '    santa.jump = santa.jump + dt*100
    'else
    '    santa.jump = 175
    'endif
    'if santa.jump <= 80 then
    '    santa.pos = 2
    'elseif santa.jump >= 175 then
    '    santa.pos = 0
    'endif
    if keydown(KEY_SPACE) and santa.pos = 0
        santa.deltay = -200
        santa.pos = 1
    elseif santa.pos
        santa.deltay = santa.deltay + dt*200
        santa.jump = santa.jump + santa.deltay*dt
        if santa.jump >= 175
            santa.jump = 175
            santa.pos = 0
        endif
    endif 
                       
    'yeti animation
    draw image yeti.walk,yeti.move,170, yeti.cell 'yeti walk
    'if yeti.cell <8 then
    '    yeti.cell = yeti.cell + dt*3
    'else
    '    yeti.cell = 0
    'endif
    yeti.cell = (yeti.cell + dt*3)%8
    if direction = 1 then                        'depends on wind direction                       
        if yeti.move < -60 then   
            yeti.move = 520
        else
            yeti.move = yeti.move - dt*20
        endif
    endif
         
    'snow animation
    if j < 3000
        direction = 1  'move from right to left
        message = "to the left"
    elseif (j > 3000 and j < 3500)
        direction = 0  'move from left to right
        message = "to the right"
    elseif j>3500
        j = 0                   
    endif
    j = j + 1
    if keydown(KEY_RIGHT) then j = 3000
    if keydown(KEY_LEFT) then j = 0
    foreach s in snow  s.Update(dt,direction) 
    foreach s in snow  s.Draw()               

    'info
    set color white
    set caret 10,235; wln "xxx"
    set caret 480,235; wln "xxx"
       
    redraw
    'wait 1
    fwait 60
wend
free music wind

I use the % (modulus) operator for the animation.

min and max just returns the smallest or largest of two numbers.