/* Basic reset so spacing behaves predictably */
* {
    box-sizing: border-box;
}

/* Page background and base layout */
body {
    margin: 0;
    min-height: 100vh;
    padding: 16px 0 24px;
    font-family: "Segoe UI", Arial, sans-serif;
    color: #1f2937;
    background:
        radial-gradient(circle at 15% 10%, rgba(147, 197, 253, 0.2) 0%, rgba(147, 197, 253, 0) 36%),
        radial-gradient(circle at 85% 90%, rgba(59, 130, 246, 0.12) 0%, rgba(59, 130, 246, 0) 42%),
        linear-gradient(180deg, #f7faff 0%, #eef3fb 100%);
}

/* Full-width wrapper for dashboard-style spacing */
.page-wrapper {
    width: 100%;
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 clamp(40px, 4vw, 56px);
}

/* Main application surface */
.app-container {
    width: 100%;
    display: grid;
    gap: 22px;
    background: rgba(255, 255, 255, 0.96);
    border: 1px solid rgba(148, 163, 184, 0.2);
    border-radius: 12px;
    padding: 28px 32px;
    box-shadow: 0 6px 16px rgba(15, 23, 42, 0.07);
}

/* Top title */
h1 {
    margin: 0;
    text-align: center;
    font-size: clamp(1.5rem, 2.7vw, 2rem);
    font-weight: 700;
}

/* Soft notification banner */
.info-banner {
    display: grid;
    grid-template-columns: auto 1fr;
    align-items: center;
    gap: 10px;
    padding: 12px 14px;
    border-radius: 12px;
    background: #f0f7ff;
    border: 1px solid #dbeafe;
}

.info-icon {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    background: #dbeafe;
    display: grid;
    place-items: center;
    font-size: 0.95rem;
}

.info-banner p {
    margin: 0;
    font-size: 0.95rem;
    color: #1e3a8a;
}

/* Two-column workspace area */
.layout-grid {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 240px;
    gap: 32px;
    align-items: start;
}

/* Keep Sudoku board centered */
.board-section {
    display: grid;
    justify-items: center;
    gap: 12px;
}

/* 9x9 board: perfect square using CSS Grid */
.sudoku-grid {
    width: min(90vw, 470px);
    aspect-ratio: 1 / 1;
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    border: 3px solid #1f2937;
    border-radius: 10px;
    overflow: hidden;
    background: #f8fbff;
}

/* Single cell style */
.cell {
    border: 1px solid #d5dfeb;
    background: rgba(255, 255, 255, 0.8);
    display: grid;
    place-items: center;
    font-size: clamp(0.95rem, 1.7vw, 1.45rem);
    font-weight: 600;
    color: #0f172a;
    user-select: none;
}

.cell.is-selected {
    outline: 2px solid #3b82f6;
    outline-offset: -2px;
    background: #eaf2ff;
}

/* Thick vertical separators for 3x3 blocks */
.cell:nth-child(9n + 3),
.cell:nth-child(9n + 6) {
    border-right: 3px solid #1f2937;
}

/* Thick horizontal separators for 3x3 blocks */
.cell:nth-child(n + 19):nth-child(-n + 27),
.cell:nth-child(n + 46):nth-child(-n + 54) {
    border-bottom: 3px solid #1f2937;
}

/* Upload box styling */
.upload-dropzone {
    width: 100%;
    min-height: 130px;
    border: 2px dashed #b8c8dd;
    border-radius: 14px;
    background: #f7fbff;
    display: grid;
    place-items: center;
    text-align: center;
    padding: 16px;
    gap: 6px;
    cursor: pointer;
    transition: background 0.2s ease, border-color 0.2s ease, box-shadow 0.2s ease;
}

.upload-placeholder {
    display: grid;
    justify-items: center;
    gap: 6px;
}

.upload-preview-image {
    display: none;
    max-width: 100%;
    max-height: 170px;
    border-radius: 10px;
    object-fit: contain;
    box-shadow: 0 4px 10px rgba(15, 23, 42, 0.1);
}

.change-image-btn {
    display: none;
    margin-top: 8px;
    border: 1px solid #c7d2e5;
    border-radius: 8px;
    background: #ffffff;
    color: #1e3a8a;
    font-size: 0.78rem;
    font-weight: 600;
    padding: 6px 10px;
    cursor: pointer;
}

.change-image-btn:hover {
    background: #eff6ff;
}

.process-image-btn {
    display: none;
    margin-top: 8px;
    border: none;
    border-radius: 8px;
    background: linear-gradient(135deg, #2563eb 0%, #3b82f6 100%);
    color: #ffffff;
    font-size: 0.8rem;
    font-weight: 600;
    padding: 7px 12px;
    cursor: pointer;
}

.process-image-btn:disabled {
    opacity: 0.65;
    cursor: not-allowed;
}

.ocr-status {
    display: none;
    margin-top: 6px;
    font-size: 0.78rem;
    color: #1e3a8a;
}

.upload-dropzone.has-image .upload-placeholder {
    display: none;
}

.upload-dropzone.has-image .upload-preview-image,
.upload-dropzone.has-image .change-image-btn,
.upload-dropzone.has-image .process-image-btn {
    display: block;
}

.upload-dropzone.is-processing .ocr-status {
    display: block;
}

.upload-dropzone:hover {
    background: #eff6ff;
    border-color: #60a5fa;
    box-shadow: 0 6px 14px rgba(59, 130, 246, 0.12);
}

.upload-icon {
    font-size: 1.5rem;
    line-height: 1;
}

.upload-title {
    font-size: 1rem;
    font-weight: 600;
    color: #1e3a8a;
}

.upload-subtext {
    font-size: 0.85rem;
    color: #64748b;
}

/* Keep the file input accessible but visually hidden */
.upload-input {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    border: 0;
}

/* Right-side control panel */
.control-panel {
    display: grid;
    gap: 22px;
    align-content: start;
}

/* Keep upload beneath solve button with balanced spacing */
.control-panel .upload-dropzone {
    margin-top: 34px;
}

/* Slightly larger board on large screens */
@media (min-width: 1400px) {
    .layout-grid {
        gap: 40px;
    }

    .sudoku-grid {
        width: min(100%, 580px);
    }
}

/* Row of circular action controls */
.top-actions {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
}

.action-item {
    display: grid;
    justify-items: center;
    gap: 8px;
}

.circle-btn {
    width: 62px;
    height: 62px;
    border: 1px solid #dde5f0;
    border-radius: 50%;
    background: #f7f9fd;
    display: grid;
    place-items: center;
    cursor: pointer;
    box-shadow: 0 4px 10px rgba(15, 23, 42, 0.08);
    transition: transform 0.15s ease, box-shadow 0.2s ease, background 0.2s ease;
}

.circle-btn:hover {
    transform: translateY(-2px);
    background: #eef4ff;
    box-shadow: 0 8px 16px rgba(15, 23, 42, 0.12);
}

.circle-btn .icon {
    font-size: 1.25rem;
    line-height: 1;
}

.action-label {
    font-size: 0.8rem;
    color: #475569;
    font-weight: 600;
}

/* 3x3 number pad */
.number-pad {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
}

.num-btn {
    height: 54px;
    border: 1px solid #d4deea;
    border-radius: 10px;
    background: #ffffff;
    font-size: 1.05rem;
    font-weight: 600;
    color: #1f2937;
    cursor: pointer;
    box-shadow: 0 3px 10px rgba(15, 23, 42, 0.08);
    transition: transform 0.15s ease, box-shadow 0.2s ease, background 0.2s ease;
}

.num-btn:hover {
    transform: translateY(-1px);
    background: #f8fbff;
    box-shadow: 0 8px 16px rgba(15, 23, 42, 0.12);
}

/* Bottom full-width solve button */
.solve-btn {
    width: 100%;
    height: 52px;
    border: none;
    border-radius: 12px;
    background: linear-gradient(135deg, #2563eb 0%, #3b82f6 100%);
    color: #ffffff;
    font-size: 1rem;
    font-weight: 700;
    cursor: pointer;
    box-shadow: 0 8px 18px rgba(37, 99, 235, 0.35);
    transition: transform 0.15s ease, box-shadow 0.2s ease, filter 0.2s ease;
}

.solve-btn:hover {
    transform: translateY(-1px);
    filter: brightness(1.03);
    box-shadow: 0 12px 20px rgba(37, 99, 235, 0.38);
}

.solve-celebration {
    position: fixed;
    top: 18px;
    right: 18px;
    z-index: 1200;
    padding: 12px 18px;
    border-radius: 999px;
    color: #ffffff;
    font-size: 0.92rem;
    font-weight: 700;
    letter-spacing: 0.2px;
    background: linear-gradient(135deg, #16a34a 0%, #22c55e 55%, #4ade80 100%);
    box-shadow: 0 10px 24px rgba(22, 163, 74, 0.35);
    animation: celebration-pop 0.35s ease-out;
}

.solve-celebration::before,
.solve-celebration::after {
    content: "";
    position: absolute;
    top: 50%;
    width: 12px;
    height: 18px;
    background: #15803d;
    transform: translateY(-50%);
}

.solve-celebration::before {
    left: -8px;
    clip-path: polygon(100% 0, 0 50%, 100% 100%);
}

.solve-celebration::after {
    right: -8px;
    clip-path: polygon(0 0, 100% 50%, 0 100%);
}

.solve-celebration.hide {
    opacity: 0;
    transform: translateY(-8px) scale(0.96);
    transition: opacity 0.4s ease, transform 0.4s ease;
}

@keyframes celebration-pop {
    0% {
        opacity: 0;
        transform: translateY(-10px) scale(0.92);
    }
    100% {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

/* Informational section below the app */
.info-content-wrap {
    width: 100%;
    padding: 26px clamp(24px, 4vw, 44px) 10px;
}

.info-content {
    max-width: 1000px;
    margin: 0 auto;
    display: grid;
    gap: 14px;
}

.content-block {
    padding: 20px 22px;
    border-radius: 12px;
    background: rgba(255, 255, 255, 0.76);
    border: 1px solid rgba(148, 163, 184, 0.2);
}

.content-block:nth-child(even) {
    background: rgba(240, 247, 255, 0.72);
}

.content-block h2 {
    margin: 0 0 10px;
    font-size: clamp(1.05rem, 2.1vw, 1.3rem);
    color: #0f172a;
}

.content-block p {
    margin: 0;
    color: #334155;
    line-height: 1.6;
}

.content-block ul {
    margin: 0;
    padding-left: 20px;
    color: #334155;
    line-height: 1.75;
}

.content-block li {
    margin-bottom: 4px;
}

.content-block li:last-child {
    margin-bottom: 0;
}

/* Responsive tweaks for smaller screens */
@media (max-width: 640px) {
    body {
        padding: 14px;
    }

    .app-container {
        padding: 16px;
        gap: 16px;
        border-radius: 14px;
    }

    .info-banner p {
        font-size: 0.9rem;
    }

    /* Stack panel below grid on smaller screens */
    .layout-grid {
        grid-template-columns: 1fr;
        gap: 16px;
    }

    .control-panel {
        width: min(100%, 470px);
        justify-self: center;
    }

    .upload-dropzone {
        min-height: 120px;
        padding: 14px;
    }

    .upload-preview-image {
        max-height: 150px;
    }

    .info-content-wrap {
        padding: 18px 14px 4px;
    }

    .content-block {
        padding: 16px;
    }
}