烟花大会：一飞冲天满天星

fx-fireworks

local Fireworks = {}
local KEY = { GRAVITY = 300, LIFE = 1.8 }

local stars = {}

function FW.Launch(x)
    local c = SL:PickColor({"red", "gold", "blue", "green", "purple"})
    local rocket = {
        x = x, y = SL:GetValue("height"),
        vy = -(360 + math.random() * 80),
        top = 50 + math.random() * 60,
        color = c, count = SL:GetValue("burstCount") or 36
    }
    SL:Schedule(function(dt)
        rocket.vy = rocket.vy + KEY.GRAVITY * dt
        rocket.y = rocket.y + rocket.vy * dt
        SL:SetFxPos("rocket", rocket.x, rocket.y)
        SL:PlayTrail("rocket_trail", rocket.x, rocket.y)
        -- 速度衰减到临界: 半空起爆
        if rocket.vy > -60 or rocket.y <= rocket.top then
            SL:UnSchedule("rocketFly")
            SL:RemoveFx("rocket")
            FW.Burst(rocket)
        end
    end, 0.016, "rocketFly")
end

function FW.Burst(r)
    SL:PlayFxAt("burst_flash", r.x, r.y)
    SL:PlaySfx("boom")
    for i = 1, r.count do
        local a = i / r.count * 6.28
        stars[#stars + 1] = {
            x = r.x, y = r.y,
            vx = math.cos(a) * (90 + math.random() * 90),
            vy = math.sin(a) * (90 + math.random() * 90),
            t = 0, c = r.color
        }
    end
    -- 星屑统一衰减
    SL:Schedule(function(dt)
        local alive = false
        for _, s in ipairs(stars) do
            if s.t < KEY.LIFE then
                alive = true
                s.t = s.t + dt
                s.vy = s.vy + 60 * dt              -- 星屑重力减半
                s.vx = s.vx * (1 - dt * 0.8)       -- 空气阻力
                s.x = s.x + s.vx * dt
                s.y = s.y + s.vy * dt
            end
        end
        if not alive then
            SL:UnSchedule("starFall")
            stars = {}
        end
    end, 0.016, "starFall")
end

return FW