import torch
from torch import nn

class SimpleCNN(nn.Module):
    def __init__(self, sample_input):
        super().__init__()
        self.features = nn.Sequential(
            nn.Conv2d(1, 16, 3, padding=1),
            nn.ReLU(),
            nn.MaxPool2d(2),
            nn.Conv2d(16, 32, 3, padding=1),
            nn.ReLU(),
            nn.MaxPool2d(2),
        )

        with torch.no_grad():
            dummy_output = self.features(sample_input.unsqueeze(0))
            self.flattened_size = dummy_output.view(1, -1).size(1)

        self.classifier = nn.Sequential(
            nn.Flatten(),
            nn.Linear(self.flattened_size, 64),
            nn.ReLU(),
            nn.Linear(64, 1)
        )

    def forward(self, x):
        x = self.features(x)
        return self.classifier(x)