吹画：一口气吹出墨梅图

 fx-inkblow

local InkBlow = {}
local branches, flowers = {}, {}

function IB.BlowBranch(src)
    -- 从枝头分出一条新枝: 角度随机偏转
    local ang = math.atan2(src.y2 - src.y1, src.x2 - src.x1)
                  + (math.random() - 0.5) * 1.4
    local len = 60 + math.random() * 40
    branches[#branches + 1] = {
        x1 = src.x2, y1 = src.y2,
        x2 = src.x2 + math.cos(ang) * len,
        y2 = src.y2 + math.sin(ang) * len,
        w = math.max(0.8, src.w - 0.8),       -- 下一代比上一代细
        gen = src.gen + 1, grow = 0
    }
    SL:PlaySfx("blow")
end

function IB.PointFlower()
    local b = branches[math.random(#branches)]
    local t = 0.3 + math.random() * 0.5
    flowers[#flowers + 1] = {
        x = b.x1 + (b.x2 - b.x1) * t,
        y = b.y1 + (b.y2 - b.y1) * t,
        r = 5 + math.random() * 3
    }
    SL:PlaySfx("dab")
end

function IB.Render(dt)
    -- 枝条: 沿生长进度画线, 宽度按代数递减
    for _, b in ipairs(branches) do
        b.grow = math.min(1, b.grow + dt * 2)
        SL:DrawBranchLine(b.x1, b.y1,
            b.x1 + (b.x2 - b.x1) * b.grow,
            b.y1 + (b.y2 - b.y1) * b.grow,
            b.w)
    end
    -- 梅花: 五瓣环绕花芯
    for _, f in ipairs(flowers) do
        for p = 1, 5 do
            SL:DrawPetal(f.x, f.y, p / 5 * 6.28, f.r / 5)
        end
        SL:DrawDot(f.x, f.y, 1.8, "#ffe2a8")
    end
end

return IB