function two_neuron_sim
% TWO_NEURON_SIM — 1 s simulation of two neurons with an excitatory synapse
%
% • Neuron A emits action potential(s) starting at t = 0.2 s.
% • Number of spikes and spike frequency are user-defined.
% • Neuron B receives an excitatory synaptic conductance from Neuron A.
% • Controls: Neuron B target voltage (V_hold), synapse strength, synapse reversal potential, playback speed.
% • Resizable UI with scrollbars. Axes are yoked (linked) in X and Y.

%% ---------- UI LAYOUT ----------
fig = uifigure('Name','Two Neuron Simulation (1 s)','Position',[100 100 980 760], ...
    'AutoResizeChildren','on');
root = uigridlayout(fig,[1 2], 'ColumnWidth',{'1x', 360}, 'RowHeight',{'1x'}, 'Scrollable','on');
root.Padding = 10; root.RowSpacing = 10; root.ColumnSpacing = 10;

% Left side: plots
left = uigridlayout(root, [2 1], 'RowHeight',{'1x','1x'}, 'ColumnWidth',{'1x'}, 'Scrollable','on');
left.Layout.Row = 1; left.Layout.Column = 1; left.Padding = 0; left.RowSpacing = 10;
ax1 = uiaxes(left); ax1.Layout.Row = 1; hold(ax1,'on');
ax2 = uiaxes(left); ax2.Layout.Row = 2; hold(ax2,'on');
linkaxes([ax1 ax2],'xy');  % yoke both axes

% Right side: controls
right = uigridlayout(root,[17 1], ...
    'RowHeight',{'fit','fit','fit','fit','fit','fit','fit','fit','fit','fit','fit','fit','fit','fit','fit','fit','1x'}, ...
    'ColumnWidth',{'1x'}, 'Scrollable','on');
right.Layout.Row = 1; right.Layout.Column = 2; right.Padding = 8; right.RowSpacing = 8;

% Title + hint
lblTitle = uilabel(right,'Text','Controls','FontWeight','bold','FontSize',14);
lblTitle.Layout.Row = 1;
hint = uilabel(right,'Text','Adjust controls then press Run.','FontColor',[0.2 0.2 0.2]);
hint.Layout.Row = 2;

% Neuron A: Number of Spikes & Frequency
lblNAS = uilabel(right,'Text','Neuron A: Number of Spikes','HorizontalAlignment','left');
lblNAS.Layout.Row = 3;
numSpikesField = uieditfield(right,'numeric','Limits',[1 50],'Value',1,'ValueDisplayFormat','%.0f');
numSpikesField.Layout.Row = 4; numSpikesField.ValueChangedFcn = @(~,~) setHint();

lblFreq = uilabel(right,'Text','Neuron A: Spike Frequency (Hz)','HorizontalAlignment','left');
lblFreq.Layout.Row = 5;
freqField = uieditfield(right,'numeric','Limits',[1 200],'Value',20,'ValueDisplayFormat','%.1f');
freqField.Layout.Row = 6; freqField.ValueChangedFcn = @(~,~) setHint();

% Neuron B Target Voltage
lblVhold = uilabel(right,'Text','Neuron B Target Voltage (mV)','HorizontalAlignment','left');
lblVhold.Layout.Row = 7;
slVhold = uislider(right, 'Limits',[-80 20], 'MajorTicks',-80:20:20, 'Value', -65);
slVhold.Layout.Row = 8;
editV = uieditfield(right,'numeric','Limits',[-120 120],'Value',-65,'ValueDisplayFormat','%.1f');
editV.Layout.Row = 9;

% Synapse Strength
lblGS = uilabel(right,'Text','Synapse Strength','HorizontalAlignment','left');
lblGS.Layout.Row = 10;
slGSyn = uislider(right, 'Limits',[0 50], 'MajorTicks',0:10:50, 'Value',5);
slGSyn.Layout.Row = 11;

% Synapse Reversal Potential
lblEs = uilabel(right,'Text','Synapse Reversal Potential (mV)','HorizontalAlignment','left');
lblEs.Layout.Row = 12;
slEsyn = uislider(right,'Limits',[-80 80],'MajorTicks',-80:20:80,'Value',0);
slEsyn.Layout.Row = 13;
editEsyn = uieditfield(right,'numeric','Limits',[-120 120],'Value',0,'ValueDisplayFormat','%.1f');
editEsyn.Layout.Row = 14;

% Playback speed control
lblSpeed = uilabel(right,'Text','Playback Speed (0.1x – 10x)','HorizontalAlignment','left');
lblSpeed.Layout.Row = 15;
slSpeed = uislider(right,'Limits',[0.1 10],'Value',1,'MajorTicks',[0.1 1 5 10]);
slSpeed.Layout.Row = 16;

% Run button
btn = uibutton(right,'Text','Run','ButtonPushedFcn',@(b,evt) runSim());
btn.FontWeight = 'bold'; btn.FontSize = 14;
btn.Layout.Row = 17;

% Callbacks
slVhold.ValueChangingFcn = @(s,evt) setHint();
slGSyn.ValueChangingFcn  = @(s,evt) setHint();
slEsyn.ValueChangingFcn  = @(s,evt) setHint();
slSpeed.ValueChangingFcn = @(s,evt) setHint();

editV.ValueChangedFcn    = @(h,evt) setSliderFromEdit(slVhold, editV);
editEsyn.ValueChangedFcn = @(h,evt) setSliderFromEdit(slEsyn, editEsyn);

slVhold.ValueChangedFcn  = @(s,evt) setEditFromSlider(editV, s);
slGSyn.ValueChangedFcn   = @(s,evt) setHint();
slEsyn.ValueChangedFcn   = @(s,evt) setEditFromSlider(editEsyn, s);

%% Axes cosmetics
setupAxes(ax1, 'Neuron A');
setupAxes(ax2, 'Neuron B');

%% Run once
runSim();

%% ---------- Utilities ----------
    function setHint
        hint.Text = 'Values changed — press Run to recompute.';
        hint.FontColor = [0.55 0.35 0.05];
    end

    function setSliderFromEdit(sl, ed)
        sl.Value = ed.Value;
        setHint();
    end

    function setEditFromSlider(ed, sl)
        ed.Value = sl.Value;
    end

    function setupAxes(ax, ttl)
        grid(ax,'on'); ax.Box = 'on';
        ax.NextPlot = 'replacechildren';
        ax.Title.String = ttl; ax.Title.FontWeight = 'bold';
        ax.XLabel.String = 'Time (ms)'; ax.YLabel.String = 'V_m (mV)';
    end

    function runSim
        % Read UI
        nSpk     = max(1, round(numSpikesField.Value));
        freqHz   = max(1, freqField.Value);
        Vhold_mV = slVhold.Value;
        gsynMax_nS = slGSyn.Value;
        Esyn_mV  = slEsyn.Value;
        speed    = slSpeed.Value;

        % Params
        T  = 1.0;          % seconds
        dt = 1e-5;         % s (0.01 ms)
        t  = 0:dt:T;
        nT = numel(t);
        C   = 200e-12;     % F
        gL  = 10e-9;       % S
        EL  = -0.065;      % V
        gClamp_nS = 20;    % fixed clamp strength (Neuron B)

        % Neuron A spikes: N spikes at freqHz starting at 0.2 s
        tsp0 = 0.2;                    % s first spike
        isi  = 1/max(freqHz, 1e-6);    % s between spikes
        spike_times = tsp0 + (0:nSpk-1)*isi;
        spike_times = spike_times(spike_times <= T - 1e-3); % keep in bounds

        V1 = EL*ones(1,nT);
        ap_dur = 0.003;    % 3 ms
        Vpeak  = 0.040;    % +40 mV
        tau1 = 0.0004; tau2 = 0.0012;  % sharp waveform
        for s = spike_times
            idx = t >= s & t <= s + ap_dur;
            tt = t(idx) - s;
            spike_w = (exp(-tt/tau2) - exp(-tt/tau1));
            spike_w = spike_w / max(spike_w + eps);
            Vcand = EL + (Vpeak - EL) * spike_w;
            V1(idx) = max(V1(idx), Vcand);
        end

        % Synapse onto Neuron B: alpha conductance per spike, summed
        tau_syn = 0.005;   % s
        gsyn = zeros(1,nT);
        for s = spike_times
            tt2 = max(t - s, 0);
            alpha = (tt2/tau_syn).*exp(1 - tt2/tau_syn);
            alpha(tt2==0) = 0;
            gsyn = gsyn + (gsynMax_nS*1e-9) * alpha;
        end
        Esyn = Esyn_mV/1000; % V

        % Neuron B
        gClamp = gClamp_nS * 1e-9; % S
        Vhold  = Vhold_mV/1000;    % V
        V2 = EL * ones(1,nT);
        for k = 1:nT-1
            Isyn   = gsyn(k) * (Esyn - V2(k));
            Iclamp = gClamp * (Vhold - V2(k));
            dV = ( -gL*(V2(k)-EL) + Isyn + Iclamp ) / C;
            V2(k+1) = V2(k) + dt * dV;
        end

        % ----- Plot & Animate -----
        ms = 1e3;
        cla(ax1); cla(ax2);
        h1 = plot(ax1, nan, nan, 'LineWidth',1.5);
        h2 = plot(ax2, nan, nan, 'LineWidth',1.5);
        yMin = floor(1e3*min([V1 V2])) - 5;  % mV
        yMax = ceil(1e3*max([V1 V2])) + 5;   % mV
        if yMin > -90, yMin = -90; end
        if yMax <  50, yMax =  50; end
        ax1.XLim = [0 T*ms]; ax2.XLim = [0 T*ms];
        ax1.YLim = [yMin yMax]; ax2.YLim = [yMin yMax];

        % Only E_syn reference on Neuron B
        yline(ax2, Esyn_mV, '--', 'E_{syn}','LabelHorizontalAlignment','left');

        % Frame pacing and stride based on speed
        target_fps = 60; frame_dt = 1/target_fps;    % s/frame (real time)
        base_step  = max(1, round(frame_dt/dt));     % samples per frame @1x
        step       = max(1, round(base_step * speed));

        for k = 1:step:nT
            set(h1,'XData', t(1:k)*ms, 'YData', V1(1:k)*1e3);
            set(h2,'XData', t(1:k)*ms, 'YData', V2(1:k)*1e3);
            drawnow limitrate;
            pause(frame_dt);
        end
        % Final high-fidelity frame
        set(h1,'XData', t*ms, 'YData', V1*1e3);
        set(h2,'XData', t*ms, 'YData', V2*1e3);
        drawnow;

        hint.Text = 'Playback complete. Adjust sliders and press Run again.';
        hint.FontColor = [0.2 0.45 0.2];
    end
end