:root {
    --primary-color: #007bff;
    --tool-bg: #f0f2f5;
    --panel-bg: #ffffff;
    --main-content-bg: #e9ecef;
    --border-color: #dee2e6;
    --text-primary: #212934;
    --text-secondary: #555;
    --text-light: #666;
    --btn-bg: #f8f9fa;
    --btn-hover-bg: #e9ecef;
    --success-color: #28a745;
}
body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: var(--tool-bg);
    color: var(--text-primary);
    margin: 0;
    padding: 20px;
    transition: background-color 0.3s ease, color 0.3s ease;
}
.container { display: flex; gap: 20px; max-width: 1440px; margin: 0 auto; height: 85vh; }
.main-content {
    flex-grow: 1; background-color: var(--main-content-bg); display: flex; justify-content: center; align-items: center;
    border-radius: 8px; position: relative; overflow: hidden; border: 1px solid var(--border-color);
}
.main-content.dragover { background-color: #dfeefe; }
.image-container { width: 100%; height: 100%; display: none; }
#image { display: block; max-width: 100%; max-height: 100%; }
.initial-state-view {
    display: flex; flex-direction: column; align-items: center; justify-content: center; text-align: center;
    color: var(--text-secondary); padding: 20px;
}
.initial-state-view .icon { font-size: 64px; line-height: 1; }
.initial-state-view h2 { font-size: 24px; color: var(--text-primary); margin: 15px 0; }
.features-list { list-style: none; padding: 0; margin: 0 0 25px 0; color: var(--text-light); line-height: 1.8; }
.initial-state-view button {
    font-size: 16px; padding: 12px 25px; background: var(--primary-color); color: white; border: none; border-radius: 5px; cursor: pointer; margin-bottom: 10px;
}
.initial-state-view p { font-size: 14px; color: #888; }
.controls-panel {
    width: 320px; flex-shrink: 0; background-color: var(--panel-bg); padding: 20px; border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05); border: 1px solid var(--border-color); display: flex; flex-direction: column; gap: 15px; transition: opacity 0.3s, background-color 0.3s ease;
}
.controls-panel.disabled { opacity: 0.5; pointer-events: none; }
h3 { margin: 0 0 10px; font-size: 16px; border-bottom: 1px solid var(--border-color); padding-bottom: 10px; }
.preview-box { width: 100%; height: 150px; overflow: hidden; border: 1px solid var(--border-color); border-radius: 4px; margin-bottom: 10px; background-color: var(--tool-bg); }
.button-group { display: grid; grid-template-columns: repeat(auto-fit, minmax(50px, 1fr)); gap: 10px; }
.button-group button, .preset-row button {
    padding: 8px; background-color: var(--btn-bg); border: 1px solid var(--border-color); color: var(--text-primary); border-radius: 4px; cursor: pointer; font-size: 15px; transition: background-color 0.2s;
}
.button-group button:hover, .preset-row button:hover { background-color: var(--btn-hover-bg); }
.resize-panel { display: flex; flex-direction: column; gap: 10px; }
.preset-row { display: grid; grid-template-columns: repeat(2, 1fr); gap: 8px; }
.size-inputs { display: grid; grid-template-columns: repeat(2, 1fr); gap: 10px; }
.size-inputs label { font-size: 13px; color: var(--text-secondary); display: flex; flex-direction: column; gap: 6px; }
.size-inputs input, .output-options select {
    padding: 8px; border-radius: 4px; border: 1px solid var(--border-color); background-color: var(--panel-bg); color: var(--text-primary); width: 100%; box-sizing: border-box;
}
.checkbox-inline { font-size: 14px; display: flex; align-items: center; gap: 8px; }
.hint { font-size: 12px; line-height: 1.5; color: var(--text-secondary); margin: 0; }
.output-options { display: flex; gap: 10px; align-items: center; }
.output-options select { flex-grow: 1; }
.download-button { background-color: var(--success-color); color: white; border: none; padding: 10px 15px; border-radius: 4px; cursor: pointer; font-weight: bold; }
body.dark-mode {
    --primary-color: #3d8bfd; --tool-bg: #1e2128; --panel-bg: #2a2e37; --main-content-bg: #111318; --border-color: #4a505f;
    --text-primary: #e5e7eb; --text-secondary: #9ca3af; --text-light: #9ca3af; --btn-bg: #373c47; --btn-hover-bg: #4a505f; --success-color: #20c997;
}
@media (max-width: 960px) {
    body { padding: 10px; }
    .container { flex-direction: column; height: auto; }
    .main-content { min-height: 50vh; }
    .controls-panel { width: auto; }
}