#!/usr/bin/env python3
"""
Eye Study Guide PDF Generator
For MBBS Physiology - Based on Guyton & Hall
"""

from reportlab.lib.pagesizes import A4
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.units import cm, mm
from reportlab.lib import colors
from reportlab.platypus import (
    SimpleDocTemplate, Paragraph, Spacer, Table, TableStyle,
    HRFlowable, PageBreak, KeepTogether
)
from reportlab.platypus.flowables import Flowable
from reportlab.lib.enums import TA_CENTER, TA_LEFT, TA_JUSTIFY
from reportlab.graphics.shapes import Drawing, Rect, String, Line, Circle, Ellipse, Polygon, Group
from reportlab.graphics import renderPDF
import urllib.request
import os

# ─── Colour palette ────────────────────────────────────────────────────────────
DARK_BLUE   = colors.HexColor('#1a3a5c')
MED_BLUE    = colors.HexColor('#2563a8')
LIGHT_BLUE  = colors.HexColor('#dbeafe')
ACCENT_TEAL = colors.HexColor('#0d9488')
LIGHT_TEAL  = colors.HexColor('#ccfbf1')
GOLD        = colors.HexColor('#b45309')
LIGHT_GOLD  = colors.HexColor('#fef3c7')
RED         = colors.HexColor('#dc2626')
LIGHT_RED   = colors.HexColor('#fee2e2')
GREEN       = colors.HexColor('#15803d')
LIGHT_GREEN = colors.HexColor('#dcfce7')
PURPLE      = colors.HexColor('#7e22ce')
LIGHT_PURPLE= colors.HexColor('#f3e8ff')
GRAY        = colors.HexColor('#6b7280')
LIGHT_GRAY  = colors.HexColor('#f3f4f6')
WHITE       = colors.white
BLACK       = colors.black

# ─── Page setup ────────────────────────────────────────────────────────────────
PAGE_W, PAGE_H = A4
MARGIN = 1.8*cm
DOC_W  = PAGE_W - 2*MARGIN

OUTPUT = '/home/daytona/workspace/eye-study-guide/Eye_Study_Guide_MBBS.pdf'

# ─── Styles ────────────────────────────────────────────────────────────────────
styles = getSampleStyleSheet()

def make_style(name, parent='Normal', **kw):
    s = ParagraphStyle(name, parent=styles[parent], **kw)
    styles.add(s)
    return s

TITLE_STYLE   = make_style('MyTitle',   fontSize=28, textColor=WHITE,
                            alignment=TA_CENTER, spaceAfter=4, fontName='Helvetica-Bold')
SUBTITLE_STYLE= make_style('MySubtitle',fontSize=13, textColor=LIGHT_BLUE,
                            alignment=TA_CENTER, spaceAfter=2, fontName='Helvetica')
H1_STYLE      = make_style('MyH1',      fontSize=15, textColor=WHITE,
                            alignment=TA_LEFT,   spaceBefore=6, spaceAfter=4,
                            fontName='Helvetica-Bold', leftIndent=0)
H2_STYLE      = make_style('MyH2',      fontSize=12, textColor=DARK_BLUE,
                            spaceBefore=10, spaceAfter=4,
                            fontName='Helvetica-Bold', leftIndent=0)
H3_STYLE      = make_style('MyH3',      fontSize=10.5, textColor=ACCENT_TEAL,
                            spaceBefore=6, spaceAfter=2,
                            fontName='Helvetica-Bold')
BODY_STYLE    = make_style('MyBody',    fontSize=9.2, textColor=BLACK,
                            spaceBefore=2, spaceAfter=2,
                            fontName='Helvetica', leading=13)
BULLET_STYLE  = make_style('MyBullet',  fontSize=9.2, textColor=BLACK,
                            spaceBefore=1, spaceAfter=1,
                            fontName='Helvetica', leftIndent=14, leading=13)
KEY_STYLE     = make_style('MyKey',     fontSize=9.2, textColor=RED,
                            fontName='Helvetica-Bold', spaceBefore=2, spaceAfter=2)
CAPTION_STYLE = make_style('MyCaption', fontSize=8, textColor=GRAY,
                            alignment=TA_CENTER, fontName='Helvetica-Oblique')
TH_STYLE      = ParagraphStyle('TH', fontSize=9, textColor=WHITE,
                                fontName='Helvetica-Bold', alignment=TA_CENTER, leading=12)
TD_STYLE      = ParagraphStyle('TD', fontSize=8.5, textColor=BLACK,
                                fontName='Helvetica', leading=11, alignment=TA_LEFT)
TD_C_STYLE    = ParagraphStyle('TDC', fontSize=8.5, textColor=BLACK,
                                fontName='Helvetica', leading=11, alignment=TA_CENTER)
TD_BOLD       = ParagraphStyle('TDB', fontSize=8.5, textColor=DARK_BLUE,
                                fontName='Helvetica-Bold', leading=11)

# ─── Helper: coloured section header ───────────────────────────────────────────
class SectionHeader(Flowable):
    def __init__(self, text, bg=DARK_BLUE, width=None, height=1.0*cm):
        super().__init__()
        self.text   = text
        self.bg     = bg
        self.width  = width or DOC_W
        self.height = height
    def wrap(self, aw, ah):
        return self.width, self.height
    def draw(self):
        c = self.canv
        c.setFillColor(self.bg)
        c.roundRect(0, 0, self.width, self.height, 5, fill=1, stroke=0)
        c.setFillColor(WHITE)
        c.setFont('Helvetica-Bold', 13)
        c.drawString(10, self.height/2 - 5, self.text)

class SubHeader(Flowable):
    def __init__(self, text, bg=MED_BLUE, width=None):
        super().__init__()
        self.text  = text
        self.bg    = bg
        self.width = width or DOC_W
    def wrap(self, aw, ah):
        return self.width, 0.75*cm
    def draw(self):
        c = self.canv
        c.setFillColor(self.bg)
        c.roundRect(0, 0, self.width, 0.75*cm, 4, fill=1, stroke=0)
        c.setFillColor(WHITE)
        c.setFont('Helvetica-Bold', 11)
        c.drawString(8, 0.75*cm/2 - 4, self.text)

class KeyBox(Flowable):
    """A coloured callout box."""
    def __init__(self, text, bg=LIGHT_GOLD, border=GOLD, width=None):
        super().__init__()
        self.text   = text
        self.bg     = bg
        self.border = border
        self.width  = width or DOC_W
        self._height= None
    def wrap(self, aw, ah):
        from reportlab.platypus import Paragraph
        p = Paragraph('★ ' + self.text, ParagraphStyle('kbp', fontSize=9,
                      fontName='Helvetica-Bold', textColor=GOLD, leading=13))
        _, h = p.wrap(self.width - 20, ah)
        self._height = h + 12
        return self.width, self._height
    def draw(self):
        c = self.canv
        c.setFillColor(self.bg)
        c.setStrokeColor(self.border)
        c.setLineWidth(1.2)
        c.roundRect(0, 0, self.width, self._height, 5, fill=1, stroke=1)
        c.setFillColor(GOLD)
        c.setFont('Helvetica-Bold', 9)
        margin = 10
        c.drawString(margin, self._height/2 - 5, '★  ' + self.text)

# ─── Helper: build a styled table ──────────────────────────────────────────────
def make_table(headers, rows, col_widths=None, header_bg=DARK_BLUE,
               alt_bg=LIGHT_BLUE, stripe_bg=WHITE):
    th_row = [Paragraph(h, TH_STYLE) for h in headers]
    data   = [th_row]
    for i, row in enumerate(rows):
        bg   = alt_bg if i % 2 == 0 else stripe_bg
        cells= []
        for cell in row:
            if isinstance(cell, str) and cell.startswith('**'):
                cells.append(Paragraph(cell.strip('*'), TD_BOLD))
            else:
                cells.append(Paragraph(str(cell), TD_STYLE))
        data.append(cells)

    if col_widths is None:
        n  = len(headers)
        col_widths = [DOC_W / n] * n

    t = Table(data, colWidths=col_widths, repeatRows=1)

    # base style
    ts = TableStyle([
        ('BACKGROUND',  (0, 0), (-1,  0),  header_bg),
        ('TEXTCOLOR',   (0, 0), (-1,  0),  WHITE),
        ('FONTNAME',    (0, 0), (-1,  0),  'Helvetica-Bold'),
        ('FONTSIZE',    (0, 0), (-1,  0),  9),
        ('ALIGN',       (0, 0), (-1,  0),  'CENTER'),
        ('VALIGN',      (0, 0), (-1, -1),  'MIDDLE'),
        ('ROWBACKGROUNDS', (0, 1), (-1, -1), [alt_bg, stripe_bg]),
        ('GRID',        (0, 0), (-1, -1),  0.5, colors.HexColor('#94a3b8')),
        ('TOPPADDING',  (0, 0), (-1, -1),  4),
        ('BOTTOMPADDING',(0,0), (-1, -1),  4),
        ('LEFTPADDING', (0, 0), (-1, -1),  5),
        ('RIGHTPADDING',(0, 0), (-1, -1),  5),
        ('ROWBACKGROUNDS', (0, 1), (-1, -1), [alt_bg, stripe_bg]),
    ])
    t.setStyle(ts)
    return t

# ─── SVG-style diagrams using ReportLab graphics ───────────────────────────────

def draw_eye_cross_section(width=DOC_W, height=220):
    """Schematic cross-section of the eyeball."""
    d = Drawing(width, height)
    cx, cy, rx, ry = width/2, height/2, width*0.30, height*0.44

    # Sclera (outer ring)
    d.add(Ellipse(cx, cy, rx+14, ry+14, fillColor=colors.HexColor('#e5e7eb'), strokeColor=DARK_BLUE, strokeWidth=2))
    # Choroid
    d.add(Ellipse(cx, cy, rx+6,  ry+6,  fillColor=colors.HexColor('#f97316'), strokeColor=colors.HexColor('#c2410c'), strokeWidth=1))
    # Retina
    d.add(Ellipse(cx, cy, rx,    ry,    fillColor=colors.HexColor('#fef9c3'), strokeColor=colors.HexColor('#ca8a04'), strokeWidth=1))

    # Vitreous humor
    d.add(Ellipse(cx, cy, rx-18, ry-18, fillColor=colors.HexColor('#eff6ff'), strokeColor=colors.HexColor('#93c5fd'), strokeWidth=1))

    # Cornea (anterior transparent bulge) - left side
    cornea_pts = [cx-rx-14, cy+30, cx-rx-28, cy, cx-rx-14, cy-30]
    d.add(Polygon(cornea_pts, fillColor=colors.HexColor('#bfdbfe'),
                  strokeColor=MED_BLUE, strokeWidth=1.5))

    # Iris
    d.add(Ellipse(cx-rx+10, cy, 8, 26, fillColor=colors.HexColor('#7c3aed'), strokeColor=DARK_BLUE, strokeWidth=1))
    # Pupil
    d.add(Ellipse(cx-rx+10, cy, 3, 12, fillColor=BLACK))

    # Lens
    pts = [cx-rx+20, cy+20, cx-rx+38, cy, cx-rx+20, cy-20]
    d.add(Polygon(pts, fillColor=colors.HexColor('#d1fae5'),
                  strokeColor=ACCENT_TEAL, strokeWidth=1.5))

    # Optic nerve (right side)
    d.add(Rect(cx+rx+14, cy-8, 30, 16, fillColor=colors.HexColor('#fde68a'), strokeColor=GOLD, strokeWidth=1))

    # Fovea dot
    d.add(Circle(cx+rx-20, cy, 5, fillColor=RED, strokeColor=RED))

    # Labels
    label_data = [
        (cx-rx-24, cy+50,  'Cornea',       MED_BLUE),
        (cx-rx+10, cy-38,  'Iris',         PURPLE),
        (cx-rx+28, cy-32,  'Lens',         ACCENT_TEAL),
        (cx, cy-ry-18,     'Sclera',       DARK_BLUE),
        (cx+20, cy-ry-8,   'Choroid',      colors.HexColor('#c2410c')),
        (cx+20, cy+ry+4,   'Retina',       colors.HexColor('#ca8a04')),
        (cx,    cy+14,     'Vitreous',     colors.HexColor('#1d4ed8')),
        (cx+rx+14, cy+22,  'Optic nerve',  GOLD),
        (cx+rx-18, cy+14,  'Fovea',        RED),
    ]
    for x, y, label, col in label_data:
        d.add(String(x, y, label, fontSize=7.5, fillColor=col,
                     fontName='Helvetica-Bold'))

    # Title
    d.add(String(width/2-80, height-12, 'FIG 1  Cross-Section of the Human Eye',
                 fontSize=9, fillColor=DARK_BLUE, fontName='Helvetica-Bold'))
    return d


def draw_retinal_layers(width=DOC_W, height=210):
    """Diagram of 10 retinal layers."""
    d = Drawing(width, height)
    layer_h = 16
    start_y = height - 30
    start_x = 80

    layers = [
        ('Inner limiting membrane',    colors.HexColor('#e0f2fe')),
        ('Nerve fibre layer',          colors.HexColor('#bae6fd')),
        ('Ganglion cell layer',        colors.HexColor('#7dd3fc')),
        ('Inner plexiform layer',      colors.HexColor('#38bdf8')),
        ('Inner nuclear layer',        colors.HexColor('#0ea5e9')),
        ('Outer plexiform layer',      colors.HexColor('#0284c7')),
        ('Outer nuclear layer',        colors.HexColor('#0369a1')),
        ('Outer limiting membrane',    colors.HexColor('#075985')),
        ('Photoreceptor layer (Rods & Cones)', colors.HexColor('#1e3a5f')),
        ('Retinal Pigment Epithelium (RPE)',   colors.HexColor('#1e1b4b')),
    ]

    for i, (name, col) in enumerate(layers):
        y = start_y - i * layer_h
        bar_w = width - start_x - 20
        # bar
        d.add(Rect(start_x, y, bar_w, layer_h-1, fillColor=col, strokeColor=WHITE, strokeWidth=0.5))
        # text colour
        tc = WHITE if i >= 5 else DARK_BLUE
        d.add(String(start_x + 5, y + 4, name, fontSize=7.5, fillColor=tc, fontName='Helvetica'))
        # number
        d.add(String(start_x - 18, y + 4, str(i+1) + '.', fontSize=7.5,
                     fillColor=DARK_BLUE, fontName='Helvetica-Bold'))

    # Arrow: LIGHT direction
    ax = start_x - 60
    d.add(Line(ax, start_y+layer_h, ax, start_y - (len(layers)-1)*layer_h,
               strokeColor=RED, strokeWidth=2))
    # arrowhead
    d.add(Polygon([ax-5, start_y-(len(layers)-1)*layer_h+8,
                   ax+5, start_y-(len(layers)-1)*layer_h+8,
                   ax,   start_y-(len(layers)-1)*layer_h],
                  fillColor=RED, strokeColor=RED))
    d.add(String(ax-22, start_y+layer_h+4, 'LIGHT', fontSize=7,
                 fillColor=RED, fontName='Helvetica-Bold'))

    d.add(String(20, height-14, 'FIG 2  Ten Layers of the Retina (Inside → Outside)',
                 fontSize=9, fillColor=DARK_BLUE, fontName='Helvetica-Bold'))
    return d


def draw_phototransduction(width=DOC_W, height=185):
    """Phototransduction cascade flowchart."""
    d = Drawing(width, height)
    steps = [
        ('LIGHT hits Rhodopsin',         DARK_BLUE),
        ('11-cis retinal → all-trans retinal', MED_BLUE),
        ('Activates TRANSDUCIN (Gt)',     ACCENT_TEAL),
        ('Activates PHOSPHODIESTERASE', ACCENT_TEAL),
        ('cGMP → 5\'-GMP  (cGMP falls)', colors.HexColor('#0369a1')),
        ('cGMP-gated channels CLOSE',    colors.HexColor('#c2410c')),
        ('Photoreceptor HYPERPOLARIZES', RED),
        ('↓ Glutamate release → Signal to brain', GREEN),
    ]
    bw, bh, gap = width*0.55, 16, 6
    sx = (width - bw) / 2
    sy = height - 20

    for i, (text, col) in enumerate(steps):
        y = sy - i*(bh + gap)
        d.add(Rect(sx, y, bw, bh, fillColor=col, strokeColor=WHITE, strokeWidth=0.5, rx=3, ry=3))
        d.add(String(sx+6, y+4, text, fontSize=7.8, fillColor=WHITE, fontName='Helvetica-Bold'))
        if i < len(steps)-1:
            mid = sx + bw/2
            d.add(Line(mid, y, mid, y-gap, strokeColor=GRAY, strokeWidth=1.5))
            d.add(Polygon([mid-4, y-gap+5, mid+4, y-gap+5, mid, y-gap],
                          fillColor=GRAY, strokeColor=GRAY))

    # Dark current box on left
    dc_x, dc_y = 5, sy - 3*(bh+gap) - 10
    d.add(Rect(dc_x, dc_y, 85, 50, fillColor=LIGHT_GOLD, strokeColor=GOLD, rx=3, ry=3))
    d.add(String(dc_x+5, dc_y+35, 'DARK CURRENT', fontSize=7.5, fillColor=GOLD, fontName='Helvetica-Bold'))
    d.add(String(dc_x+5, dc_y+25, 'cGMP high →', fontSize=7, fillColor=BLACK))
    d.add(String(dc_x+5, dc_y+15, 'channels OPEN', fontSize=7, fillColor=BLACK))
    d.add(String(dc_x+5, dc_y+5,  'Vm = -40 mV', fontSize=7, fillColor=BLACK))

    d.add(String(10, height-12, 'FIG 3  Phototransduction Cascade',
                 fontSize=9, fillColor=DARK_BLUE, fontName='Helvetica-Bold'))
    return d


def draw_visual_pathway(width=DOC_W, height=230):
    """Schematic of the visual pathway."""
    d = Drawing(width, height)

    # Two eyes at top
    for ex, label in [(width*0.28, 'LEFT EYE'), (width*0.72, 'RIGHT EYE')]:
        d.add(Ellipse(ex, height-22, 30, 15, fillColor=LIGHT_BLUE, strokeColor=DARK_BLUE, strokeWidth=1.5))
        d.add(Circle(ex, height-22, 7, fillColor=DARK_BLUE))
        d.add(String(ex-22, height-10, label, fontSize=7, fillColor=DARK_BLUE, fontName='Helvetica-Bold'))

    # Optic nerves down to chiasm
    chiasm_y = height - 70
    for ex in [width*0.28, width*0.72]:
        d.add(Line(ex, height-37, width/2, chiasm_y, strokeColor=MED_BLUE, strokeWidth=2))

    # Chiasm box
    d.add(Rect(width/2-40, chiasm_y-12, 80, 24, fillColor=LIGHT_PURPLE,
               strokeColor=PURPLE, rx=4, ry=4))
    d.add(String(width/2-28, chiasm_y-4, 'Optic Chiasm', fontSize=8, fillColor=PURPLE, fontName='Helvetica-Bold'))

    # Optic tracts
    lgn_y = chiasm_y - 60
    left_lgn_x  = width*0.22
    right_lgn_x = width*0.78
    d.add(Line(width/2, chiasm_y-12, left_lgn_x,  lgn_y+20, strokeColor=MED_BLUE, strokeWidth=2))
    d.add(Line(width/2, chiasm_y-12, right_lgn_x, lgn_y+20, strokeColor=MED_BLUE, strokeWidth=2))

    # Cross-over lines
    d.add(Line(width*0.28, height-37, right_lgn_x, lgn_y+20, strokeColor=colors.HexColor('#93c5fd'), strokeWidth=1.5, strokeDashArray=[3,2]))
    d.add(Line(width*0.72, height-37, left_lgn_x,  lgn_y+20, strokeColor=colors.HexColor('#93c5fd'), strokeWidth=1.5, strokeDashArray=[3,2]))

    # LGN boxes
    for lx, label in [(left_lgn_x, 'Left LGN'), (right_lgn_x, 'Right LGN')]:
        d.add(Rect(lx-28, lgn_y, 56, 20, fillColor=LIGHT_TEAL, strokeColor=ACCENT_TEAL, rx=3, ry=3))
        d.add(String(lx-22, lgn_y+5, label, fontSize=7.5, fillColor=ACCENT_TEAL, fontName='Helvetica-Bold'))

    # Optic radiation to cortex
    ctx_y = lgn_y - 55
    for lx in [left_lgn_x, right_lgn_x]:
        d.add(Line(lx, lgn_y, lx, ctx_y+20, strokeColor=MED_BLUE, strokeWidth=2))

    # Visual cortex boxes
    for lx, label in [(left_lgn_x, 'Left V1 Cortex'), (right_lgn_x, 'Right V1 Cortex')]:
        d.add(Rect(lx-38, ctx_y, 76, 20, fillColor=LIGHT_RED, strokeColor=RED, rx=3, ry=3))
        d.add(String(lx-32, ctx_y+5, label, fontSize=7.5, fillColor=RED, fontName='Helvetica-Bold'))

    # Annotation: nasal fibres cross
    d.add(String(width/2+6, chiasm_y+10, '← Nasal fibres cross', fontSize=6.5, fillColor=PURPLE))

    # Calcarine note
    d.add(String(left_lgn_x-38, ctx_y-12, 'Calcarine fissure (Brodmann 17)',
                 fontSize=6.5, fillColor=GRAY))

    d.add(String(10, height-12, 'FIG 4  Visual Pathway (Both Eyes)',
                 fontSize=9, fillColor=DARK_BLUE, fontName='Helvetica-Bold'))
    return d


def draw_dark_adaptation(width=DOC_W*0.7, height=165):
    """Simplified dark adaptation curve."""
    d = Drawing(width, height)
    ox, oy = 45, 20
    pw, ph  = width - 55, height - 40

    # Axes
    d.add(Line(ox, oy, ox, oy+ph, strokeColor=DARK_BLUE, strokeWidth=1.5))
    d.add(Line(ox, oy, ox+pw, oy, strokeColor=DARK_BLUE, strokeWidth=1.5))

    # Axis labels
    d.add(String(ox+pw/2-30, 2, 'Minutes in Dark', fontSize=8, fillColor=DARK_BLUE))
    for i, v in enumerate([0, 10, 20, 30, 40]):
        x = ox + i*(pw/4)
        d.add(String(x-4, oy-11, str(v), fontSize=7, fillColor=DARK_BLUE))
        d.add(Line(x, oy-3, x, oy+3, strokeColor=DARK_BLUE, strokeWidth=1))
    d.add(String(2, oy+ph/2-10, 'Retinal', fontSize=7, fillColor=DARK_BLUE))
    d.add(String(2, oy+ph/2-20, 'Sensitivity', fontSize=7, fillColor=DARK_BLUE))

    # Cone curve (first 10 min, small rise)
    cone_pts = []
    for t in range(0, 11):
        x = ox + t*(pw/40)
        y = oy + min(t*3.5, 35)
        cone_pts.extend([x, y])

    # Rod curve (continues and rises steeply)
    rod_pts = []
    for t in range(0, 41):
        x = ox + t*(pw/40)
        # log-like growth
        import math
        y = oy + min(math.log(t+1)*22, ph-5)
        rod_pts.extend([x, y])

    # Draw as polyline
    from reportlab.graphics.shapes import PolyLine
    d.add(PolyLine(cone_pts, strokeColor=ACCENT_TEAL, strokeWidth=2.5))
    d.add(PolyLine(rod_pts,  strokeColor=RED,         strokeWidth=2.5))

    # Labels
    d.add(String(ox+pw*0.12, oy+38, 'Cone', fontSize=7.5, fillColor=ACCENT_TEAL, fontName='Helvetica-Bold'))
    d.add(String(ox+pw*0.12, oy+28, 'adaptation', fontSize=7, fillColor=ACCENT_TEAL))
    d.add(String(ox+pw*0.6,  oy+ph*0.7, 'Rod adaptation', fontSize=7.5, fillColor=RED, fontName='Helvetica-Bold'))
    d.add(String(ox+pw*0.6,  oy+ph*0.6, '(slow, large)', fontSize=7, fillColor=RED))

    # Key values
    d.add(String(ox+pw*0.85, oy+15, '25,000×', fontSize=7.5, fillColor=RED, fontName='Helvetica-Bold'))

    d.add(String(0, height-12, 'FIG 5  Dark Adaptation Curve',
                 fontSize=9, fillColor=DARK_BLUE, fontName='Helvetica-Bold'))
    return d


def draw_visual_field_defects(width=DOC_W, height=190):
    """Visual field defect diagram."""
    d = Drawing(width, height)

    sites = [
        ('Optic nerve',      'Monocular blindness',            width*0.15, height-30),
        ('Optic chiasm',     'Bitemporal hemianopia',           width*0.38, height-30),
        ('Optic tract',      'Contralateral homonymous\nhemianopia', width*0.62, height-30),
        ('Visual cortex',    'Homonymous hemianopia\n+ macular sparing', width*0.85, height-30),
    ]
    for site, effect, x, y in sites:
        d.add(Rect(x-40, y-12, 80, 24, fillColor=LIGHT_BLUE, strokeColor=MED_BLUE, rx=4, ry=4))
        d.add(String(x-36, y-2, site, fontSize=7.5, fillColor=DARK_BLUE, fontName='Helvetica-Bold'))
        d.add(String(x-36, y-40, effect, fontSize=7, fillColor=RED))

    # Dividing arrows
    for i in range(len(sites)-1):
        x1 = sites[i][2]+42
        x2 = sites[i+1][2]-42
        y0 = height-18
        d.add(Line(x1, y0, x2, y0, strokeColor=GRAY, strokeWidth=1, strokeDashArray=[4,2]))
        d.add(Polygon([x2-4, y0+3, x2-4, y0-3, x2, y0], fillColor=GRAY, strokeColor=GRAY))

    d.add(String(10, height-12, 'FIG 6  Visual Field Defects by Site of Lesion',
                 fontSize=9, fillColor=DARK_BLUE, fontName='Helvetica-Bold'))
    return d


# ─── Cover page background ─────────────────────────────────────────────────────
class CoverBackground(Flowable):
    def __init__(self, w, h):
        super().__init__()
        self._w, self._h = w, h
    def wrap(self, aw, ah):
        return self._w, self._h
    def draw(self):
        c = self.canv
        c.setFillColor(DARK_BLUE)
        c.rect(0, 0, self._w, self._h, fill=1, stroke=0)
        # decorative circles
        import math
        for r, alpha in [(200, 0.08), (130, 0.1), (70, 0.12)]:
            c.setFillColorRGB(0.5, 0.8, 1, alpha=alpha)
            c.circle(self._w*0.85, self._h*0.85, r, fill=1, stroke=0)
        c.setFillColor(DARK_BLUE)  # reset

# ─── Build document ────────────────────────────────────────────────────────────
def build():
    doc = SimpleDocTemplate(
        OUTPUT, pagesize=A4,
        leftMargin=MARGIN, rightMargin=MARGIN,
        topMargin=MARGIN, bottomMargin=MARGIN,
        title='Eye Study Guide - MBBS Physiology',
        author='Orris AI | Based on Guyton & Hall'
    )

    story = []
    SP = Spacer(1, 0.25*cm)
    SP2 = Spacer(1, 0.5*cm)

    # ── COVER ──────────────────────────────────────────────────────────────────
    story.append(CoverBackground(PAGE_W - 2*MARGIN, PAGE_H - 2*MARGIN))
    # Adjust: cover is a background flowable; put text over it using a table
    # Instead, render cover as a full-page block
    # Use a table with coloured background for cover
    cover_data = [[
        Paragraph('<b>THE EYE</b>', ParagraphStyle('CT', fontSize=36,
                  textColor=WHITE, alignment=TA_CENTER, fontName='Helvetica-Bold',
                  spaceAfter=8)),
    ], [
        Paragraph('Complete Study Guide for MBBS Physiology', ParagraphStyle('CS',
                  fontSize=15, textColor=LIGHT_BLUE, alignment=TA_CENTER,
                  fontName='Helvetica')),
    ], [
        Paragraph('Anatomy · Optics · Retina · Phototransduction<br/>'
                  'Visual Pathway · Disorders', ParagraphStyle('CS2',
                  fontSize=11, textColor=colors.HexColor('#93c5fd'),
                  alignment=TA_CENTER, fontName='Helvetica', leading=16)),
    ], [
        Spacer(1, 0.5*cm),
    ], [
        Paragraph('Source: Guyton &amp; Hall Textbook of Medical Physiology, 13th Ed',
                  ParagraphStyle('CS3', fontSize=9, textColor=colors.HexColor('#94a3b8'),
                  alignment=TA_CENTER, fontName='Helvetica-Oblique')),
    ]]
    cover_table = Table(cover_data, colWidths=[DOC_W])
    cover_table.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,-1), DARK_BLUE),
        ('ALIGN', (0,0), (-1,-1), 'CENTER'),
        ('VALIGN', (0,0), (-1,-1), 'MIDDLE'),
        ('TOPPADDING', (0,0), (-1,-1), 18),
        ('BOTTOMPADDING', (0,0), (-1,-1), 18),
        ('ROUNDEDCORNERS', [8]),
    ]))
    story.append(Spacer(1, 3*cm))
    story.append(cover_table)
    story.append(PageBreak())

    # ── SECTION 1: ANATOMY ─────────────────────────────────────────────────────
    story.append(SectionHeader('1.  ANATOMY OF THE EYE'))
    story.append(SP2)

    # Eye diagram
    story.append(draw_eye_cross_section())
    story.append(Paragraph('Figure 1 - Schematic cross-section of the human eyeball showing major structures.',
                            CAPTION_STYLE))
    story.append(SP2)

    story.append(SubHeader('1.1  Three Coats (Layers) of the Eyeball', bg=MED_BLUE))
    story.append(SP)

    layers_table = make_table(
        ['Layer', 'Components', 'Key Function'],
        [
            ['Outer fibrous coat', 'Sclera (posterior 5/6) + Cornea (anterior 1/6)', 'Protection; light entry via cornea'],
            ['Middle vascular coat\n(Uvea)', 'Choroid + Ciliary body + Iris', 'Nutrition; accommodation; pupil control'],
            ['Inner neural coat', 'Retina (posterior 2/3)', 'Phototransduction; image processing'],
        ],
        col_widths=[DOC_W*0.28, DOC_W*0.40, DOC_W*0.32],
    )
    story.append(layers_table)
    story.append(SP2)

    story.append(SubHeader('1.2  Key Structures', bg=MED_BLUE))
    story.append(SP)

    structs = [
        ['Cornea', 'Transparent; avascular; nourished by aqueous humor; provides ~40 D (2/3 of total refractive power)'],
        ['Sclera', 'White opaque outer coat; continuous with cornea anteriorly'],
        ['Iris', 'Pigmented; sphincter pupillae (miosis - PS, CN III); dilator pupillae (mydriasis - sympathetic). Pupil size changes cause 16× change in light entering'],
        ['Ciliary body', 'Secretes aqueous humor; controls lens curvature via zonular fibers during accommodation'],
        ['Lens', 'Transparent biconvex; 20 D in relaxed state; increases to 34 D (max accommodation = 14 D in children)'],
        ['Choroid', 'Vascular; nourishes outer retina and RPE'],
        ['Retina', 'Neural layer; rods + cones + interneurons; inverted (light must pass through inner layers first)'],
        ['Fovea', '0.3 mm; only cones; inner layers displaced laterally → maximum acuity'],
        ['Optic disc', 'Blind spot; no photoreceptors; where optic nerve exits'],
        ['Aqueous humor', 'Clear, protein-free; produced by ciliary body at 2-3 µL/min; nourishes cornea & iris; drains via Canal of Schlemm'],
        ['Vitreous humor', 'Gelatinous; between lens and retina; proteoglycan network; maintains eye shape'],
    ]
    struct_table = make_table(
        ['Structure', 'Key Features'],
        structs,
        col_widths=[DOC_W*0.23, DOC_W*0.77],
        alt_bg=LIGHT_BLUE, stripe_bg=WHITE
    )
    story.append(struct_table)
    story.append(SP)
    story.append(KeyBox('Pupil diameter variation causes up to 16-FOLD change in the amount of light reaching the retina. (Guyton)', LIGHT_GOLD, GOLD))
    story.append(SP2)

    # Aqueous humor flow
    story.append(SubHeader('1.3  Aqueous Humor Flow & IOP', bg=MED_BLUE))
    story.append(SP)
    aq_flow = make_table(
        ['Step', 'Location', 'Detail'],
        [
            ['Produced', 'Ciliary body (epithelium)', 'Active secretion; 2-3 µL/min'],
            ['Flows into', 'Posterior chamber', 'Behind iris, in front of lens'],
            ['Passes through', 'Pupil', 'Anterior chamber (in front of iris)'],
            ['Drains via', 'Trabecular meshwork', '→ Canal of Schlemm → venous system'],
            ['Normal IOP', '12-20 mmHg (avg 15)', 'Measured by tonometry'],
        ],
        col_widths=[DOC_W*0.22, DOC_W*0.32, DOC_W*0.46],
        header_bg=ACCENT_TEAL, alt_bg=LIGHT_TEAL, stripe_bg=WHITE
    )
    story.append(aq_flow)
    story.append(PageBreak())

    # ── SECTION 2: RETINA ──────────────────────────────────────────────────────
    story.append(SectionHeader('2.  THE RETINA'))
    story.append(SP2)

    story.append(draw_retinal_layers())
    story.append(Paragraph('Figure 2 - Ten layers of the retina. Light enters from inside (bottom) and must pass through inner layers before reaching photoreceptors.',
                            CAPTION_STYLE))
    story.append(SP2)

    story.append(SubHeader('2.1  Ten Layers of the Retina (Inside → Outside)', bg=MED_BLUE))
    story.append(SP)
    ret_layers = make_table(
        ['#', 'Layer', 'Contents / Note'],
        [
            ['1', 'Inner limiting membrane', 'Innermost; first layer light enters'],
            ['2', 'Nerve fibre layer (Stratum opticum)', 'Axons of ganglion cells → optic nerve'],
            ['3', 'Ganglion cell layer', 'Only output neurons of retina; fire true APs'],
            ['4', 'Inner plexiform layer', 'Bipolar ↔ Ganglion cell synapses; amacrine cells'],
            ['5', 'Inner nuclear layer', 'Bipolar cells, horizontal cells, amacrine cells'],
            ['6', 'Outer plexiform layer', 'Photoreceptor ↔ Bipolar cell synapses; horizontal cells'],
            ['7', 'Outer nuclear layer', 'Cell bodies (nuclei) of rods and cones'],
            ['8', 'Outer limiting membrane', '—'],
            ['9', 'Photoreceptor layer', 'Outer segments of rods and cones (face choroid)'],
            ['10', 'Retinal Pigment Epithelium (RPE)', 'Absorbs light; recycles retinal; phagocytoses shed discs'],
        ],
        col_widths=[DOC_W*0.06, DOC_W*0.37, DOC_W*0.57],
        header_bg=DARK_BLUE, alt_bg=LIGHT_BLUE, stripe_bg=WHITE
    )
    story.append(ret_layers)
    story.append(SP2)

    story.append(SubHeader('2.2  Rods vs Cones - Comparison Table', bg=MED_BLUE))
    story.append(SP)
    rvc = make_table(
        ['Feature', 'RODS', 'CONES'],
        [
            ['Number',           '~120 million',             '~6 million'],
            ['Location',         'Peripheral retina',        'Macula / fovea'],
            ['Vision type',      'Scotopic (dim/night)',     'Photopic (bright/day)'],
            ['Colour vision',    'No (achromatic)',          'Yes (3 types)'],
            ['Acuity',           'Low',                      'High (highest in fovea)'],
            ['Photopigment',     'Rhodopsin\n(retinal + Scotopsin)', 'Iodopsin\n(retinal + Photopsin)'],
            ['Convergence',      'High (~100 rods:1 ganglion)', '~1:1 in fovea'],
            ['Sensitivity',      'Very high',                'Lower'],
            ['Adaptation speed', 'Slow (30-40 min)',         'Fast (7-10 min)'],
            ['Protein defect\n(deficiency)', 'Night blindness\n(Vitamin A deficit)', 'Colour blindness\n(X-linked, opsins)'],
        ],
        col_widths=[DOC_W*0.28, DOC_W*0.36, DOC_W*0.36],
        header_bg=DARK_BLUE, alt_bg=LIGHT_BLUE, stripe_bg=WHITE
    )
    story.append(rvc)
    story.append(PageBreak())

    # ── SECTION 3: OPTICS ──────────────────────────────────────────────────────
    story.append(SectionHeader('3.  OPTICS OF THE EYE'))
    story.append(SP2)

    story.append(SubHeader('3.1  Refractive Power', bg=MED_BLUE))
    story.append(SP)
    ref_data = make_table(
        ['Component', 'Refractive Index', 'Power (Diopters)', 'Notes'],
        [
            ['Cornea (anterior surface)', '1.38', '~40 D', 'Contributes 2/3 of total power; most powerful'],
            ['Aqueous humor', '1.33', '—', 'Separates cornea from lens'],
            ['Crystalline lens', '1.40 (avg)', '20 D (relaxed)\nup to 34 D (max accommodation)', 'Variable - provides accommodation'],
            ['Vitreous humor', '1.34', '—', 'Fills posterior segment'],
            ['TOTAL (relaxed eye)', '—', '59 DIOPTERS', '"Reduced eye" - single surface 17 mm from retina'],
        ],
        col_widths=[DOC_W*0.28, DOC_W*0.18, DOC_W*0.26, DOC_W*0.28],
        header_bg=ACCENT_TEAL, alt_bg=LIGHT_TEAL, stripe_bg=WHITE
    )
    story.append(ref_data)
    story.append(SP)
    story.append(KeyBox('Total refractive power = 59 D. Cornea provides 2/3 (~40 D). Lens provides 1/3 (20 D) but is the variable component (accommodation).', LIGHT_TEAL, ACCENT_TEAL))
    story.append(SP2)

    story.append(SubHeader('3.2  Refractive Errors', bg=MED_BLUE))
    story.append(SP)
    ref_err = make_table(
        ['Error', 'Defect', 'Cause', 'Correction'],
        [
            ['Emmetropia', 'Normal - image on retina', 'Normal eye', 'None'],
            ['Myopia\n(Nearsightedness)', 'Image in FRONT of retina', 'Eyeball too long or lens too convex', 'CONCAVE\n(diverging) lens'],
            ['Hypermetropia\n(Farsightedness)', 'Image BEHIND retina', 'Eyeball too short or lens too flat', 'CONVEX\n(converging) lens'],
            ['Astigmatism', 'Different focal lengths in different planes', 'Irregular corneal curvature', 'Cylindrical lens'],
            ['Presbyopia', 'Reduced accommodation', 'Lens loses elasticity with age (~45+)', 'Convex reading glasses'],
        ],
        col_widths=[DOC_W*0.22, DOC_W*0.26, DOC_W*0.30, DOC_W*0.22],
        header_bg=DARK_BLUE, alt_bg=LIGHT_BLUE, stripe_bg=WHITE
    )
    story.append(ref_err)
    story.append(SP2)

    story.append(SubHeader('3.3  Accommodation', bg=MED_BLUE))
    story.append(SP)
    acc_bullets = [
        '• For near objects: Ciliary muscle CONTRACTS → Zonular fibers RELAX → Lens becomes more CONVEX → ↑ refractive power',
        '• Maximum accommodation in children = 14 diopters (lens power increases from 20 D to 34 D)',
        '• Presbyopia = lens stiffens with age → accommodation lost (~45 years)',
        '• NEAR RESPONSE TRIAD: (1) Accommodation (2) Convergence of eyes (3) Miosis (pupil constriction)',
        '• All three components mediated by CN III (oculomotor) via parasympathetic pathway',
    ]
    for b in acc_bullets:
        story.append(Paragraph(b, BULLET_STYLE))
    story.append(PageBreak())

    # ── SECTION 4: PHOTOTRANSDUCTION ──────────────────────────────────────────
    story.append(SectionHeader('4.  PHOTOTRANSDUCTION'))
    story.append(SP2)

    story.append(draw_phototransduction())
    story.append(Paragraph('Figure 3 - Phototransduction cascade. Light triggers rhodopsin activation leading to photoreceptor hyperpolarization.',
                            CAPTION_STYLE))
    story.append(SP2)

    story.append(SubHeader('4.1  Rhodopsin Visual Cycle', bg=MED_BLUE))
    story.append(SP)
    rhod = make_table(
        ['Component', 'Detail'],
        [
            ['Rhodopsin composition', '11-cis RETINAL + SCOTOPSIN (protein)'],
            ['Location', 'Outer segment discs of RODS; ~40% concentration'],
            ['Light effect', '11-cis retinal → ALL-TRANS retinal → Opsin separation'],
            ['Intermediate products', 'Bathorhodopsin → Lumirhodopsin → Metarhodopsin I → Metarhodopsin II (activates Transducin)'],
            ['Regeneration', 'All-trans retinal → Vitamin A (retinol) → 11-cis retinal (in RPE) → Rhodopsin'],
            ['Vitamin A deficiency', 'Cannot regenerate rhodopsin → NIGHT BLINDNESS (Nyctalopia)'],
            ['Cone pigment', 'IODOPSIN = retinal + PHOTOPSIN (3 variants: red/green/blue)'],
        ],
        col_widths=[DOC_W*0.30, DOC_W*0.70],
        header_bg=DARK_BLUE, alt_bg=LIGHT_BLUE, stripe_bg=WHITE
    )
    story.append(rhod)
    story.append(SP2)

    story.append(SubHeader('4.2  Ionic Basis (Dark Current)', bg=MED_BLUE))
    story.append(SP)
    ionic = make_table(
        ['State', 'cGMP level', 'Na⁺ channels', 'Membrane potential', 'Glutamate release'],
        [
            ['DARK', 'HIGH', 'OPEN (dark current)', '-40 mV (depolarized)', 'Continuous (high)'],
            ['LIGHT', 'LOW (PDE degrades it)', 'CLOSED', '-70 mV (hyperpolarized)', 'Decreased'],
        ],
        col_widths=[DOC_W*0.12, DOC_W*0.17, DOC_W*0.23, DOC_W*0.26, DOC_W*0.22],
        header_bg=MED_BLUE, alt_bg=LIGHT_BLUE, stripe_bg=WHITE
    )
    story.append(ionic)
    story.append(SP)
    story.append(KeyBox('KEY EXAM POINT: Photoreceptors HYPERPOLARIZE (not depolarize) in response to light. Only ganglion cells generate true propagated action potentials.', LIGHT_RED, RED))
    story.append(SP2)

    story.append(SubHeader('4.3  Colour Vision', bg=MED_BLUE))
    story.append(SP)
    colour = make_table(
        ['Cone Type', 'Opsin', 'Peak Wavelength', 'Perceived Colour'],
        [
            ['S-cones (Short)',  'Blue photopsin',  '~430 nm', 'BLUE'],
            ['M-cones (Medium)', 'Green photopsin', '~530 nm', 'GREEN'],
            ['L-cones (Long)',   'Red photopsin',   '~560-570 nm', 'RED'],
        ],
        col_widths=[DOC_W*0.22, DOC_W*0.26, DOC_W*0.26, DOC_W*0.26],
        header_bg=DARK_BLUE, alt_bg=LIGHT_BLUE, stripe_bg=WHITE
    )
    story.append(colour)
    story.append(SP)
    story.append(Paragraph('• Trichromatic theory (Young-Helmholtz): Colour perception from ratio of activation of 3 cone types', BULLET_STYLE))
    story.append(Paragraph('• Colour blindness: X-linked recessive; usually red-green deficiency; more common in males', BULLET_STYLE))
    story.append(PageBreak())

    # ── SECTION 5: LIGHT & DARK ADAPTATION ────────────────────────────────────
    story.append(SectionHeader('5.  LIGHT & DARK ADAPTATION'))
    story.append(SP2)

    story.append(draw_dark_adaptation())
    story.append(Paragraph('Figure 5 - Dark adaptation curve. Note the inflection at ~7-10 min (cones adapt first, rods adapt more slowly but achieve far greater sensitivity).',
                            CAPTION_STYLE))
    story.append(SP2)

    adapt_data = make_table(
        ['Parameter', 'Cones', 'Rods'],
        [
            ['Adaptation speed', 'Fast (~7-10 min)', 'Slow (30-40 min)'],
            ['Max sensitivity gain', 'Moderate', '~25,000-fold'],
            ['Photopigment involved', 'Iodopsin', 'Rhodopsin'],
            ['Mechanism', 'Photopsin regeneration', 'Rhodopsin regeneration + Vitamin A recycling'],
            ['Scotopic / Photopic', 'Photopic only', 'Scotopic (takes over after cones plateau)'],
        ],
        col_widths=[DOC_W*0.30, DOC_W*0.35, DOC_W*0.35],
        header_bg=DARK_BLUE, alt_bg=LIGHT_BLUE, stripe_bg=WHITE
    )
    story.append(adapt_data)
    story.append(SP)
    story.append(KeyBox('After 1 min in dark: 10× sensitivity. After 20 min: ~6,000×. After 40 min: ~25,000×. Two phases in curve = cones (early) + rods (late).', LIGHT_GOLD, GOLD))
    story.append(PageBreak())

    # ── SECTION 6: VISUAL PATHWAY ─────────────────────────────────────────────
    story.append(SectionHeader('6.  VISUAL PATHWAY & CENTRAL PROCESSING'))
    story.append(SP2)

    story.append(draw_visual_pathway())
    story.append(Paragraph('Figure 4 - Visual pathway. Nasal fibres cross at the optic chiasm; temporal fibres remain ipsilateral.',
                            CAPTION_STYLE))
    story.append(SP2)

    vp_steps = make_table(
        ['Station', 'Structure', 'Key Points'],
        [
            ['1st', 'Retinal ganglion cells', 'Only neurons that generate APs; axons form optic nerve (CN II)'],
            ['2nd', 'Optic chiasm', 'Nasal fibres CROSS to opposite side; temporal fibres stay ipsilateral'],
            ['3rd', 'Optic tract', 'Contains fibres from BOTH eyes representing same visual hemifield'],
            ['4th', 'Dorsal LGN (thalamus)', '6 layers: M-cells (1,2) = motion/depth; P-cells (3-6) = colour/detail. Two eyes kept separate.'],
            ['5th', 'Optic radiation', 'Geniculocalcarine tract. Upper radiation (parietal); Lower = Meyers loop (temporal)'],
            ['6th', 'Primary visual cortex (V1)', 'Calcarine fissure, medial occipital lobe, Brodmann area 17. Fovea has disproportionately large representation.'],
        ],
        col_widths=[DOC_W*0.08, DOC_W*0.28, DOC_W*0.64],
        header_bg=DARK_BLUE, alt_bg=LIGHT_BLUE, stripe_bg=WHITE
    )
    story.append(vp_steps)
    story.append(SP2)

    story.append(SubHeader('6.1  LGN Layers', bg=MED_BLUE))
    story.append(SP)
    lgn = make_table(
        ['Layers', 'Cell Type', 'Input from', 'Function'],
        [
            ['1, 2', 'Magnocellular (M)', 'Large ganglion cells (Y-cells)', 'Motion, depth, coarse form, low contrast'],
            ['3, 4, 5, 6', 'Parvocellular (P)', 'Small ganglion cells (X-cells)', 'Fine detail, colour, high acuity, texture'],
        ],
        col_widths=[DOC_W*0.15, DOC_W*0.25, DOC_W*0.30, DOC_W*0.30],
        header_bg=ACCENT_TEAL, alt_bg=LIGHT_TEAL, stripe_bg=WHITE
    )
    story.append(lgn)
    story.append(SP2)

    story.append(SubHeader('6.2  Other Visual Projections (Guyton)', bg=MED_BLUE))
    story.append(SP)
    other_proj = [
        '• Suprachiasmatic nucleus (hypothalamus) → Circadian rhythm control (day/night synchronisation)',
        '• Pretectal nuclei (midbrain) → PUPILLARY LIGHT REFLEX; reflex focusing movements',
        '• Superior colliculus → Rapid eye movements (saccades) toward sudden peripheral visual stimuli',
        '• Ventral LGN/basal areas → Behavioural responses to visual stimuli',
    ]
    for b in other_proj:
        story.append(Paragraph(b, BULLET_STYLE))
    story.append(PageBreak())

    # ── SECTION 7: VISUAL FIELD DEFECTS ───────────────────────────────────────
    story.append(SectionHeader('7.  VISUAL FIELD DEFECTS'))
    story.append(SP2)

    story.append(draw_visual_field_defects())
    story.append(Paragraph('Figure 6 - Visual field defects at different sites of lesion along the visual pathway.',
                            CAPTION_STYLE))
    story.append(SP2)

    vfd = make_table(
        ['Site of Lesion', 'Visual Field Defect', 'Key Cause'],
        [
            ['One optic nerve', 'Monocular blindness (same eye)', 'Optic neuritis, trauma, MS'],
            ['Optic chiasm (central/midline)', 'BITEMPORAL HEMIANOPIA\n(tunnel vision)', 'Pituitary adenoma (commonest cause)'],
            ['Optic chiasm (lateral)', 'Monocular nasal hemianopia', 'Carotid artery aneurysm'],
            ['Optic tract', 'Contralateral HOMONYMOUS\nHEMIANOPIA', 'Stroke, tumour'],
            ['Upper optic radiation (parietal lobe)', 'Contralateral lower quadrantanopia', 'Parietal lobe infarct'],
            ['Lower optic radiation -\nMeyer\'s loop (temporal lobe)', '"PIE IN THE SKY"\nContralateral upper quadrantanopia', 'Temporal lobe lesion / TLE surgery'],
            ['Visual cortex (occipital)', 'Contralateral homonymous hemianopia\nwith MACULAR SPARING', 'Posterior cerebral artery infarct'],
        ],
        col_widths=[DOC_W*0.33, DOC_W*0.38, DOC_W*0.29],
        header_bg=RED, alt_bg=LIGHT_RED, stripe_bg=WHITE
    )
    story.append(vfd)
    story.append(SP)
    story.append(KeyBox('Macular sparing in cortical lesions: Dual blood supply (PCA + MCA) to the occipital pole. Also, the macula has large cortical representation over a wide area.', LIGHT_GOLD, GOLD))
    story.append(PageBreak())

    # ── SECTION 8: EYE MOVEMENTS ──────────────────────────────────────────────
    story.append(SectionHeader('8.  EYE MOVEMENTS'))
    story.append(SP2)

    em = make_table(
        ['Type', 'Description', 'Control Centre', 'Purpose'],
        [
            ['Saccades', 'Rapid jumps, 2-3/sec; brain suppresses vision during saccade', 'Frontal eye fields + Superior colliculus', 'Move fovea rapidly to new target'],
            ['Smooth pursuit', 'Follows moving object; velocity-matched; requires cortical computation', 'Parieto-occipital cortex + Cerebellum', 'Keep moving object on fovea'],
            ['Vergence\n(Convergence/Divergence)', 'Both eyes move toward/away from each other', 'CN III (medial rectus)', 'Binocular fixation on near/far objects'],
            ['Vestibulo-ocular\nreflex (VOR)', 'Head moves → eyes move opposite direction', 'Vestibular nuclei + CN III/IV/VI', 'Stabilize image during head movement'],
            ['Optokinetic\nnystagmus', 'Slow tracking + fast saccadic reset', 'Brainstem', 'Track large moving field'],
        ],
        col_widths=[DOC_W*0.20, DOC_W*0.30, DOC_W*0.26, DOC_W*0.24],
        header_bg=DARK_BLUE, alt_bg=LIGHT_BLUE, stripe_bg=WHITE
    )
    story.append(em)
    story.append(PageBreak())

    # ── SECTION 9: PUPILLARY LIGHT REFLEX ────────────────────────────────────
    story.append(SectionHeader('9.  PUPILLARY LIGHT REFLEX'))
    story.append(SP2)

    plr = make_table(
        ['Component', 'Pathway'],
        [
            ['AFFERENT (sensory)', 'Retina → Optic nerve (CN II) → Pretectal nucleus (midbrain) - BILATERAL projection'],
            ['EFFERENT (motor)', 'Edinger-Westphal nucleus → CN III → Ciliary ganglion → Constrictor pupillae'],
            ['Direct reflex', 'Illuminated eye constricts'],
            ['Consensual reflex', 'Opposite (non-illuminated) eye also constricts (because pretectal nucleus projects bilaterally)'],
            ['RAPD\n(Marcus Gunn pupil)', 'Relative Afferent Pupillary Defect - swinging light test: affected eye DILATES instead of constricting. Indicates AFFERENT pathway defect (optic nerve or retinal disease)'],
            ['Argyll Robertson pupil', 'Accommodates but does NOT react to light. Lesion in pretectal area. Classically syphilis.'],
        ],
        col_widths=[DOC_W*0.28, DOC_W*0.72],
        header_bg=DARK_BLUE, alt_bg=LIGHT_BLUE, stripe_bg=WHITE
    )
    story.append(plr)
    story.append(PageBreak())

    # ── SECTION 10: QUICK REVISION TABLE ─────────────────────────────────────
    story.append(SectionHeader('10.  QUICK REVISION - HIGH-YIELD FACTS'))
    story.append(SP2)

    quick_rev = make_table(
        ['Key Fact', 'Value / Answer'],
        [
            ['Total refractive power of eye (relaxed)',  '59 DIOPTERS'],
            ['Corneal contribution',                      '~40 D (2/3 of total)'],
            ['Lens contribution (relaxed)',               '20 D'],
            ['Maximum accommodation',                    '14 D (children); lens goes 20→34 D'],
            ['Aqueous humor production rate',            '2-3 µL/min (by ciliary body)'],
            ['Normal intraocular pressure (IOP)',        '12-20 mmHg (average 15 mmHg)'],
            ['Number of rods',                           '~120 million'],
            ['Number of cones',                          '~6 million'],
            ['Fovea diameter',                           '0.3 mm; only cones'],
            ['Dark adaptation - full sensitivity',       '~40 minutes (rods)'],
            ['Dark adaptation - fold increase',         '~25,000-fold'],
            ['Rod photopigment',                        'Rhodopsin = 11-cis retinal + SCOTOPSIN'],
            ['Cone photopigment',                       'Iodopsin = retinal + PHOTOPSIN (3 types)'],
            ['Retinal cell that fires APs',             'Ganglion cells ONLY'],
            ['Response of photoreceptors to light',     'HYPERPOLARIZATION (dark current closes)'],
            ['Site of Rhodopsin regeneration',          'Retinal Pigment Epithelium (RPE)'],
            ['Vitamin A deficiency → eye',              'Night blindness (Nyctalopia)'],
            ['Visual cortex location',                  'Calcarine fissure, Brodmann area 17'],
            ['LGN layers (magnocellular)',               'Layers 1 & 2 (motion, depth)'],
            ['LGN layers (parvocellular)',               'Layers 3,4,5,6 (colour, fine detail)'],
            ['Bitemporal hemianopia → cause',           'Pituitary adenoma (optic chiasm)'],
            ['Macular sparing → lesion at',             'Visual cortex (PCA infarct)'],
            ['Meyer\'s loop defect',                    '"Pie in sky" - upper quadrantanopia'],
            ['Near response triad',                     'Accommodation + Convergence + Miosis'],
            ['Glaucoma - first-line drug',              'Prostaglandin analogue (e.g. Latanoprost)'],
            ['Glaucoma type - most common',             'Primary Open-Angle Glaucoma (POAG)'],
            ['Argyll Robertson pupil - cause',          'Syphilis (neurosyphilis) - pretectal lesion'],
        ],
        col_widths=[DOC_W*0.52, DOC_W*0.48],
        header_bg=GOLD, alt_bg=LIGHT_GOLD, stripe_bg=WHITE
    )
    story.append(quick_rev)
    story.append(SP2)

    # ── FINAL BOX ─────────────────────────────────────────────────────────────
    final = Table([[
        Paragraph('This study guide is based on <b>Guyton &amp; Hall Textbook of Medical Physiology, 13th Edition</b>.<br/>'
                  'Compiled by <b>Orris AI</b> for MBBS Physiology exam preparation.',
                  ParagraphStyle('ft', fontSize=8, textColor=WHITE, alignment=TA_CENTER,
                                 fontName='Helvetica', leading=12))
    ]], colWidths=[DOC_W])
    final.setStyle(TableStyle([
        ('BACKGROUND', (0,0), (-1,-1), DARK_BLUE),
        ('ALIGN', (0,0), (-1,-1), 'CENTER'),
        ('TOPPADDING', (0,0), (-1,-1), 10),
        ('BOTTOMPADDING', (0,0), (-1,-1), 10),
        ('ROUNDEDCORNERS', [6]),
    ]))
    story.append(final)

    doc.build(story)
    print(f'✅  PDF created: {OUTPUT}')

if __name__ == '__main__':
    build()

Successfully replaced 1 instance(s) of the string in '/home/daytona/workspace/eye-study-guide/create_eye_pdf.py'