Color wheel example

AddCSLuaFile()
ENT.Type = "anim"
ENT.AutomaticFrameAdvance = true

ENT.Model = "models/wheel.mdl"
ENT.Segments = 32
ENT.StartFrame = 356
ENT.FrameCount = 360

-- Ordered table of colors
ENT.Colors = {
    "red", -- Red is the first segment in rotation
    "black"
}

function ENT:Initialize()
    self:SetModel(self.Model)

    local uFrameCount = self.FrameCount

    if (uFrameCount < 1) then
        error(string.format("expected ENT.FrameCount >= 1, got %d", uFrameCount))
    end

    local uStartFrame = self.StartFrame

    if (uStartFrame < 0 or uStartFrame > uFrameCount) then
        error(string.format("expected ENT.StartFrame [0, %u), got %d", uFrameCount, uStartFrame))
    end

    local uColors = #self.Colors

    if (uColors == 0) then
        error("expected #ENT.Colors >= 1, got 0")
    end

    -- Cache these since they're constant

    -- How many frames is each segment touching the needle
    self.m_nFramesPerSegment = uFrameCount / self.Segments

    -- How many frames between StartFrame and FrameCount
    self.m_uFrameDelta = uFrameCount - uStartFrame

    -- Number of colors
    self.m_uColors = uColors
end

function ENT:StartRotation()
    -- Do maths here for determining how fast/how long your wheel will be travelling
    -- Use ENT.StartFrame to start the wheel in the exact center
    -- Call self:StopRotation() when the spinning is done
end

function ENT:StopRotation()
    -- Call this when the rotation has finished

    local uStartFrame = self.StartFrame
    local uFrameCount = self.FrameCount

    -- Cycle is [0, 1] where 0 is frame 0 (not FrameStart), and 1 is FrameCount - 1
    -- Convert this to frame numbers so the value can be put in a proper range
    local uFrame = math.Remap(self:GetCycle(), 0, 1, 0, uFrameCount - 1)

    -- Now adjust the frame to be relative to FrameStart
    -- Frames start at 0 so the last frame is FrameCount - 1
    if (uFrame >= uStartFrame) then
        -- If the frame is greater than StartFrame,
        -- these are the starting frames
        uFrame = uFrame - uStartFrame
    else
        -- If the frame is less than StartFrame,
        -- the value has cycled back around and needs to be raised
        -- with the distance between StartFrame and FrameCount
        uFrame = uFrame + self.m_uFrameDelta
    end

    -- Map the localised frame value to a percentage [0, 1)
    local uColor = self:GetWinningColor(math.Remap(uFrame, 0, uFrameCount, 0, 1))

    -- Do whatever you need to with winning here
    -- uColor is an index in the Colors table

    -- Example
    print(string.format("Landed on color %s!", self.Colors[uColor]))
end

-- Takes a number [0, 1)
function ENT:GetWinningColor(uCycle)
    -- Calculates the color at whatever frame the wheel has stopped rotating on
    -- Remap the value one more time into the range [0, SegmentCount) to get the
    -- segment the wheel stopped on, then put it in range of the repeating colors
    return math.floor(math.Remap(uCycle, 0, 1, 0, self.Segments)) % self.m_uColors + 1
end

function ENT:Think()
    self:NextThink(CurTime())

    return true
end