rain drops lobster

drops.lobster

import std
import vec
import color
import gl

// Window settings
let SCREEN_WIDTH = 700.0
let SCREEN_HEIGHT = 700.0
let WINDOW_TITLE = "Rain"

// Colors (Lobster uses 0.0-1.0 for color components)
let BACKGROUND_COLOR = float4 { 25.0/255.0, 35.0/255.0, 55.0/255.0, 1.0 }
let RAIN_BASE_COLOR_RGB = float3 { 200.0/255.0, 200.0/255.0, 220.0/255.0 }

// Rain parameters
let MIN_DROPS = 50
let MAX_DROPS = 100
let MIN_DROP_LENGTH = 10.0
let MAX_DROP_LENGTH = 20.0
let MIN_DROP_SPEED = 100.0
let MAX_DROP_SPEED = 300.0
let MIN_ALPHA = 128.0 / 255.0 // 50% opacity
let MAX_ALPHA = 178.0 / 255.0 // 70% opacity

class Drop:
    x:float = rnd_float() * SCREEN_WIDTH
    y:float = rnd_float() * -SCREEN_HEIGHT
    length:float = rnd_float() * (MAX_DROP_LENGTH - MIN_DROP_LENGTH) + MIN_DROP_LENGTH
    speed:float = rnd_float() * (MAX_DROP_SPEED - MIN_DROP_SPEED) + MIN_DROP_SPEED
    color_with_alpha:float4 = float4 { RAIN_BASE_COLOR_RGB.x, RAIN_BASE_COLOR_RGB.y, RAIN_BASE_COLOR_RGB.z, rnd_float() * (MAX_ALPHA - MIN_ALPHA) + MIN_ALPHA }

    def init_drop():
        x = rnd_float() * SCREEN_WIDTH
        y = rnd_float() * -SCREEN_HEIGHT
        length = rnd_float() * (MAX_DROP_LENGTH - MIN_DROP_LENGTH) + MIN_DROP_LENGTH
        speed = rnd_float() * (MAX_DROP_SPEED - MIN_DROP_SPEED) + MIN_DROP_SPEED
        color_with_alpha = float4 { RAIN_BASE_COLOR_RGB.x, RAIN_BASE_COLOR_RGB.y, RAIN_BASE_COLOR_RGB.z, rnd_float() * (MAX_ALPHA - MIN_ALPHA) + MIN_ALPHA }

    def update(delta_time:float):
        y += speed * delta_time
        if y > SCREEN_HEIGHT:
            init_drop()

    def draw():
        gl.color(color_with_alpha)
        gl.line(float2 { x, y }, float2 { x, y + length }, 1.0)


def main():
    fatal(gl.window(WINDOW_TITLE, int(SCREEN_WIDTH), int(SCREEN_HEIGHT)))
    gl.set_target_delta_time(1.0 / 60.0)

    let num_drops = rnd(MAX_DROPS - MIN_DROPS + 1) + MIN_DROPS
    var drops:[Drop] = []
    for(num_drops):
        drops.push(Drop {})

    while gl.frame() and gl.button("escape") != 1:
        let delta_time = gl.delta_time()

        for(drops) drop:
            drop.update(delta_time)

        gl.clear(BACKGROUND_COLOR)

        for(drops) drop:
            drop.draw()

main()